audiohal: Make sure audio data transfer related commands go via FMQ

When outputting audio, the framework issues several HAL calls
from the same thread that writes into data FMQ. These calls
also need to be served on the same thread that writes audio data
to HAL. The same thing happens when audio input is commenced.

Add a command FMQ for passing different commands to the HAL thread.
This way, depending on the calling thread, the same call may go
either via hwbinder or via the command queue.

This dramatically reduces jitter in RTT measurements (although
doesn't improve the latency).

Bug: 30222631
Test: scripted RTT app
Change-Id: I04c826e2479d8210fd9c99756241156cda3143b6