AudioManager: add API for muting playback until device connects

Introduce API to implement the feature where playback is
muted until a specific device connects. The muting call
is accompanied by a timeout after which muted players
are unmuted.
Implementation:
- AudioManager: API, management of events sent by AudioService
- AudioService: tracks presence/absence of audio device that
  drives the muting, permission check
- PlaybackActivityMonitor: mutes/unmutes existing players,
  mutes new players when created, keeps track of timeout.

Bug: 200218901
Test: atest com.google.android.gts.audioservice.AudioServiceHostTest#testMuteAwaitConnection

Change-Id: I014c542e5b74402a41081326a53ec9d7552db021