Allow BluetoothAudioPortImpl to inherit caller's thread priority.

This help BT HAL's function calls from AudioFlinger's writer thread to
get processed without much delay, resulting in reduced audio glitches.

Bug: 335049159
Bug: 308712263
Flag: com.android.bluetooth.flags.audio_port_binder_inherit_rt
Test: mmm packages/modules/Bluetooth/system/audio_hal_interface

Change-Id: I8884ed996945976a3c1eb7e9226ae891907b066b