BT Audio support using primary HAL

- Added BT extension to support audio playback via primary output.
  The BT extension exposes APIs to commicate with the BT device for
  audio playback
  The BT extension uses the BT IPC interfaces in order to communicate
  with the BT devices.

Change-Id: I53e642a778dbe74e3e0030a81a19c001b7560d16