bluetooth: Introduce hci_connect_sco

hci_connect is a super function for connecting hci protocols. But the SCO mode
parameter is only needed by SCO. The security requirements are not needed for
SCO channels. It makes sense to have a separate function.
Bluetooth: Parameters for outgoing SCO connections

In order to establish a transparent SCO connection, the correct settings must
be specified in the SetupSynchronousConnection request. For that, a bit is set
in ACL connection flags to set up the desired parameters. If this bit is not
set, a legacy SCO connection will be requested.
This patch uses T2 settings.
Bluetooth: Fallback transparent SCO from T2 to T1

When initiating a transparent eSCO connection, make use of T2 settings at
first try. T2 is the recommended settings from HFP 1.6 WideBand Speech. Upon
connection failure, try T1 settings.
To know which of T2 or T1 should be used, the connection attempt index is used.
T2 failure is detected if Synchronous Connection Complete Event fails with
error 0x0d. This error code has been found experimentally by sending a T2
request to a T1 only SCO listener. It means "Connection Rejected due to
Limited resource".
Bluetooth: Add enhanced mode for SCO sockets

The enhanced mode is designed to support CSA2 specification. To set it, caller
must have made sure that requested settings are supported by hardware. This
can be done by reading hardware options using management commands.
Bluetooth: declare Core Spec Addendum 2 commands

CSA2 specification declares 3 additional HCI commands:
1. Enhanced Setup Synchronous Connection,
   This command can add or modify a synchronous connection.
2. Enhanced Accept Synchronous Connection Request,
   This command is used to accept a synchronous connection.
3. Read Local Supported Codecs
   This commands retrieves supported codecs on an adapter.
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