ao_wasapi: Use OPT_STRING_VALIDATE for device suboption

Validates by trying to pick the device using the device enumerator and
aborting with out of range on failure.

Refactors find_and_load_device to not use the wasapi_state; it might be
called during validation. Adds missing CoInitialize/CoUninitialize calls.
Remove unused variables (the SAFE_RELEASE macros keep them referenced so
compiler warnings don't help finding them...).

Remove the IMMDeviceEnumerator from the wasapi_state, it's only needed
during initialization and initialization is now well factored enough to
get rid of it.

Try and connect to unplugged devices as well when using the device ID
string.
ao_wasapi: Change function macros to require semicolon after invocation

Add semicolons where they were missing.
ao_wasapi: Don't search for devices as part of validation

This could turn valid parameters into syntax errors by the mere presence
or abscence of a device (e.g. USB audio devices), so don't do that.

We do validate that, if the parameter is an integer, it is not negative.
We also respond to the "help" parameter, which does the same as the "list"
suboption but exits after listing.

Demote the validation logging to MSGL_DBG2.
ao_wasapi: Support loading devices by name

Do an strstr match against the device description and, if we have only
a single match, take it. This works as long as the devices in the system
don't change, but it's not supposed to be reliable; if one wants
reliability, one uses the device ID string.

Formatting.