audio policy: default routing rules for BLE audio devices

Add default audio routing rules for BLE audio devices in audio
policy manager engine.

Also remove isA2dpSupported() helper: checking if a2dp is supported
before selecting an A2DP device is redundant as the device connection
would have been rejected in the first place if A2DP was not supported.

The implementation for communication use cases is not final until a new API is
added to control routing to BLE audio similarly to what exists for
Bluetooth SCO or speakerphone.

Bug: 161358428
Test: regression on audio playback and capture routing, especially with
hearing aid, Bluetooth A2DP and Bluetooth SCO.

Change-Id: If07150dc4495aeee5e796d891fd3ce98965bf5f9
Merged-In: If07150dc4495aeee5e796d891fd3ce98965bf5f9