libnm-core: drop nm_setting_lookup_type_by_quark()

nm_setting_lookup_type_by_quark() was only ever used in places that
were still mistakenly assuming the old style of nm_connection_verify()
errors, where the error message would contain only a property name and
no further explanation. Fix those places to assume that the error will
contain a real error message, and include both the setting name and
the property name.

Given that, there's no longer any need for
nm_setting_lookup_type_by_quark(), so drop it.
libnm-core: clean up NMConnectionError

Rename NM_CONNECTION_ERROR_UNKNOWN to NM_CONNECTION_ERROR_FAILED,
following GError best practices.

Replace NM_CONNECTION_ERROR_CONNECTION_SETTING_NOT_FOUND ("no
NMSettingConnection") with a more generic
NM_CONNECTION_ERROR_MISSING_SETTING. Use that new code in a few places
that had previously been using NM_CONNECTION_ERROR_SETTING_NOT_FOUND,
which was supposed to mean "the setting that you asked about doesn't
exist", not "the connection is invalid because it's missing a required
setting".

Clarify that NM_CONNECTION_ERROR_INVALID_SETTING can be used for any
"invalid or inappropriate NMSetting", not just a "conflicting" one.
(But fix a case in nm_connection_update_secrets() that was returning
INVALID_SETTING when it should have been return-if-failing instead.)

For both MISSING_SETTING and INVALID_SETTING, always prefix the error
message with "setting-name: ", just like we do with the various
NMSetting MISSING_PROPERTY and INVALID_PROPERTY errors. And make sure
that the error message is marked for localization.

Drop NM_CONNECTION_ERROR_CONNECTION_TYPE_INVALID, which is pretty
pointless; it was only used in the case where connection.type was the
name of a valid setting type that is not a base setting type. Instead,
just return NM_SETTING_CONNECTION_ERROR_INVALID_PROPERTY for
connection.type in this case (which is what the code already did when
connection.type was completely unrecognized).
libnm-core: merge NMSetting*Error into NMConnectionError

Each setting type was defining its own error type, but most of them
had exactly the same three errors ("unknown", "missing property", and
"invalid property"), and none of the other values was of much use
programmatically anyway.

So, this commit merges NMSettingError, NMSettingAdslError, etc, all
into NMConnectionError. (The reason for merging into NMConnectionError
rather than NMSettingError is that we also already have
"NMSettingsError", for errors related to the settings service, so
"NMConnectionError" is a less-confusable name for settings/connection
errors than "NMSettingError".)

Also, make sure that all of the affected error messages are localized,
and (where appropriate) prefix them with the relevant property name.

Renamed error codes:

NM_SETTING_ERROR_PROPERTY_NOT_FOUND -> NM_CONNECTION_ERROR_PROPERTY_NOT_FOUND
NM_SETTING_ERROR_PROPERTY_NOT_SECRET -> NM_CONNECTION_ERROR_PROPERTY_NOT_SECRET

Remapped error codes:

NM_SETTING_*_ERROR_MISSING_PROPERTY -> NM_CONNECTION_ERROR_MISSING_PROPERTY
NM_SETTING_*_ERROR_INVALID_PROPERTY -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_ERROR_PROPERTY_TYPE_MISMATCH -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_BLUETOOTH_ERROR_TYPE_SETTING_NOT_FOUND -> NM_CONNECTION_ERROR_INVALID_SETTING
NM_SETTING_BOND_ERROR_INVALID_OPTION -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_BOND_ERROR_MISSING_OPTION -> NM_CONNECTION_ERROR_MISSING_PROPERTY
NM_SETTING_CONNECTION_ERROR_TYPE_SETTING_NOT_FOUND -> NM_CONNECTION_ERROR_MISSING_SETTING
NM_SETTING_CONNECTION_ERROR_SLAVE_SETTING_NOT_FOUND -> NM_CONNECTION_ERROR_MISSING_SETTING
NM_SETTING_IP4_CONFIG_ERROR_NOT_ALLOWED_FOR_METHOD -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_IP6_CONFIG_ERROR_NOT_ALLOWED_FOR_METHOD -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_VLAN_ERROR_INVALID_PARENT -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_WIRELESS_SECURITY_ERROR_MISSING_802_1X_SETTING -> NM_CONNECTION_ERROR_MISSING_SETTING
NM_SETTING_WIRELESS_SECURITY_ERROR_LEAP_REQUIRES_802_1X -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_WIRELESS_SECURITY_ERROR_LEAP_REQUIRES_USERNAME -> NM_CONNECTION_ERROR_MISSING_PROPERTY
NM_SETTING_WIRELESS_SECURITY_ERROR_SHARED_KEY_REQUIRES_WEP -> NM_CONNECTION_ERROR_INVALID_PROPERTY
NM_SETTING_WIRELESS_ERROR_CHANNEL_REQUIRES_BAND -> NM_CONNECTION_ERROR_MISSING_PROPERTY

Dropped error codes (were previously defined but unused):

NM_SETTING_CDMA_ERROR_MISSING_SERIAL_SETTING
NM_SETTING_CONNECTION_ERROR_IP_CONFIG_NOT_ALLOWED
NM_SETTING_GSM_ERROR_MISSING_SERIAL_SETTING
NM_SETTING_PPP_ERROR_REQUIRE_MPPE_NOT_ALLOWED
NM_SETTING_PPPOE_ERROR_MISSING_PPP_SETTING
NM_SETTING_SERIAL_ERROR_MISSING_PPP_SETTING
NM_SETTING_WIRELESS_ERROR_MISSING_SECURITY_SETTING
libnm-core: fix up/simplify NMCryptoError

Many of NMCryptoError's codes would basically never be useful for
programs to distinguish between. Streamline the codes, and fix the
enumeration member names to start with "NM_CRYPTO_ERROR_" rather than
"NM_CRYPTO_ERR_".
libnm-core: add nm-errors.[ch]

Add nm-errors.[ch], and move libnm-core's two error domains
(NMConnectionError and NMCryptoError) there.

NMCryptoError wasn't previously visible, but it can be returned from
some public API, so it should be.
libnm-core, core: register NMConnectionError with D-Bus

Register NMConnectionError with D-Bus on both sides, so that, eg,
connection validation failures in the daemon will translate to the
correct error codes in the client.
libnm: drop unused NMRemoteConnectionError

NMRemoteConnection used to return
NM_REMOTE_CONNECTION_ERROR_DISCONNECTED if you tried to operate on a
connection that had been disconnected from its D-Bus proxy. But this
disappeared in the gdbus port (since gdbus doesn't emit a signal when
it happens, so it's harder to notice. And it's not clear why
NMRemoteConnection did this when no other class did anyway...).
libnm: merge device-type-specific errors into NMDeviceError

As with the settings, each device type was defining its own error
type, containing either redundant or non-useful error codes. Drop all
of the subtype-specific errors, and reduce things to just
NM_DEVICE_ERROR_FAILED, NM_DEVICE_ERROR_INCOMPATIBLE_CONNECTION, and
NM_DEVICE_ERROR_INVALID_CONNECTION.

The device-type-specific errors were only returned from their
nm_device_connection_compatible() implementations, so this is also a
good opportunity to simplify those, by moving duplicated functionality
into the base NMDevice implementation, and then allowing the
subclasses to assume that the connection has already been validated in
their own code. Most of the implementations now just check that the
connection has the correct type for the device (which can't be done at
the NMDevice level since some device types (eg, Ethernet) support
multiple connection types.)

Also, make sure that all of the error messages are localized.
libnm-core, libnm, devices: merge client and daemon NMDeviceError

Merge libnm's NMDeviceError and the daemon's NMDeviceError into a
single enum (in nm-errors.h). Register the domain with D-Bus, and add
a test that the client side decodes it correctly.

The daemon's NM_DEVICE_ERROR_CONNECTION_INVALID gets absorbed into
libnm's NM_DEVICE_ERROR_INVALID_CONNECTION, and
NM_DEVICE_ERROR_UNSUPPORTED_DEVICE_TYPE gets dropped, since it was
only returned from one place, which is now using
NM_DEVICE_ERROR_FAILED, since (a) it ought to be a "can't happen", and
(b) the only caller of that function just logs error->message and then
frees the error without ever looking at the code.
devices: drop device-type-specific error domains

Most NMDevice types defined their own error domain but then never used
it. A few did use their errors, but some of those errors are redundant
with NMDeviceError, and others can be added to it.
libnm-core, core: move NMManagerError to nm-errors

Move the definition of NMManagerError to nm-errors, register it with
D-Bus, and verify in the tests that it maps correctly.

NM_MANAGER_ERROR_INTERNAL gets renamed to NM_MANAGER_ERROR_FAILED for
consistency. NM_MANAGER_ERROR_UNMANAGED_DEVICE is dropped since that
name doesn't really describe the one place it was previously used in.
NM_MANAGER_ERROR_SYSTEM_CONNECTION is dropped because it was't being
used. NM_MANAGER_ERROR_UNSUPPORTED_CONNECTION_TYPE is dropped because
it can be replaced with an NM_CONNECTION_ERROR.
NM_MANAGER_ERROR_AUTOCONNECT_NOT_ALLOWED is turned into the more
generic NM_MANAGER_ERROR_CONNECTION_NOT_AVAILABLE.

Also, remove the <tp:possible-errors> sections from nm-manager.xml,
since they were completely out of date.
libnm-core, core: merge NMLoggingError into NMManagerError

NMManagerError has other operation-specific errors (like
NM_MANAGER_ERROR_ALREADY_ASLEEP_OR_AWAKE), so it makes sense to move
NM_LOGGING_ERROR_UNKNOWN_LEVEL and NM_LOGGING_ERROR_UNKNOWN_DOMAIN
there too rather than having them in their own tiny error domain.
libnm-core, settings: move NMSettingsError to nm-errors

Move the definition of NMSettingsError to nm-errors, register it with
D-Bus, and verify in the tests that it maps correctly.

Remove a few unused error codes, simplify a few others, and rename
GENERAL to FAILED and HOSTNAME_INVALID to INVALID_HOSTNAME, for
consistency.
settings: drop plugin-specific error domains

Each plugin defined its own error domain, though none actually defined
any errors. Replace these with appropriate uses of
NM_SETTINGS_ERROR_INVALID_CONNECTION and NM_SETTINGS_ERROR_FAILED.
libnm-core, settings: move NMAgentManagerError to nm-errors

Move the definition of NMAgentManagerError to nm-errors, register it
with D-Bus, and verify in the tests that it maps correctly.
libnm-core, libnm, settings: move NMSecretAgentError to nm-errors

Move the definition of NMSecretAgentError to nm-errors, register it
with D-Bus, and verify in the tests that it maps correctly.

NM_SECRET_AGENT_ERROR_INTERNAL_ERROR is renamed to
NM_SECRET_AGENT_ERROR_FAILED, and NM_SECRET_AGENT_ERROR_NOT_AUTHORIZED
to NM_SECRET_AGENT_ERROR_PERMISSION_DENIED, for consistency with other
error domains. While NMSecretAgentError, unlike most other error
domains, has always been correctly mapped across D-Bus, the renaming
is not an ABI break, because the daemon never checks for either of
those values, so all versions of the daemon will treat
"org.freedesktop.NetworkManager.SecretAgent.InternalError" and
"org.freedesktop.NetworkManager.SecretAgent.Failed" the same (by just
ignoring the error name and keeping only the error message).
libnm-core, libnm: move NMVpnPluginError to nm-errors

Move the definition of NMVpnPluginError to nm-errors and register it
with D-Bus. Rename GENERAL to FAILED, and CONNECTION_INVALID to
INVALID_CONNECTION, for consistency.

(As with the NMSecretAgentError renamings, the renaming here is not an
ABI break, because the daemon currently never checks for any specific
error codes other than INTERACTIVE_NOT_SUPPORTED.)
libnm: drop _nm_dbus_register_error_domain()

All D-Bus error domains are registered from libnm-core now.
libnm: strip GDBus gunk from GErrors

Call g_dbus_error_strip_remote_error() on all errors returned from
gdbus calls. (Blah!)
libnm: consolidate NMClientError and NMObjectError

Consolidate NMClientError and NMObjectError (such that there is now
only one libnm-API-specific error domain). In particular, merge
NM_CONNECTION_ERROR_CONNECTION_REMOVED with
NM_OBJECT_ERROR_OBJECT_CREATION_FAILURE as the new
NM_CONNECTION_ERROR_OBJECT_CREATION_FAILED.

Also make object_creation_failed() be a plain method rather than a
signal, since there's no reason for anyone to be connecting to it on
another object. And remove its GError argument because the subclass
can just create its own more-specific error.