Add audio channel of Bluetooth Audio Hal v2 for Hearing Aid

This brings a new interface for Hearing Aid to communicate with audio.
Both audio control and data path go through the new Bluetooth audio
HAL and is similar to A2DP usecase. It initials this interface of client
side and get audio provider at setup and manage session with audio hal.

There is a system property to switch between the UIPC socket and the
Bluetooth Audio Hal v2 interface:
    persist.bluetooth.bluetooth_audio_hal.enabled

Bug: 111519504
Bug: 120222104
Test: manual test with Hearing Aid
TODO: Pass audio matadata into Hearing Aid service

Change-Id: I648775d61a8a4fe4fa680dd31ffc39fc89267c06