Send playback mute events from audio server

The events are sent by the AudioFlinger which communicates directly
through oneway ipc methods with the AudioService. The mute reasons are
described with a PersistableBundle to keep the interface generic for future
extensions.

Test: dumpsys audio
Bug: 235521198
Change-Id: I82cf7100a80e3fc71b629739ce5a5701ab3afc84