Add support for mmap stream

Add support for MMAP streams created by Oboe service.
- A new audio thread class MmapThread deriving from ThreadBase
is added to manage permissions, volume, routing and wakelocks for activity
on MMAP streams.
- Requests received over MmapStreamInterface to open, start and stop
a MMAP stream are forwarded to audio policy manager so that activity
on MMAP capture and playback streams is visible to audio policy and
taken into account in volume and routing management.
`

Bug: Bug: 33398120
Test: manual test
Change-Id: I957906495fe9277d2972d810b633f50cd1e14ec3