audioflinger: implement Bluetooth latency mode control

Generalize latency mode control previously
only implemented on spatializer thread to mixer threads.
For mixer threads, latency mode control is used when a
Bluetooth A2DP or LE audio device is selected and the
audio HAL stream supports sevreal latency modes.

The following methods and class members are moved from
SpatializerThread class to MixerThread class:
  - onHalLatencyModesChanged_l()
  - getSupportedLatencyModes()
  - mSetLatencyMode
  - mSupportedLatencyModes

setHalLatencyMode_l() has a different implementation in
SpatializerThread and MixerThread.

Test: make
Bug: 257922898
Change-Id: I25106fcb7c3dd9fdeabfbbe29941c7cd3be22196