audioflinger: define MMAP HAL Stream control interface

Added definition of MmapStreamInterface used by Oboe service
to open, configure and control MMAP streams at the audio HAl.

This interface is implemented by audioflinger and abstracts the details
of interacting with audio policy manager and audio HAL from Oboe service.

A callback interface MmapStreamCallback is also defiend to communicate
volume and routing changes back to Oboe service.

Bug: 33398120
Test: build
Change-Id: If953d44903aaa4eb17ff16f1922ca16e5e0e0a87