AudioService: Make suspended apps lose audio focus

Handle ACTION_PACKAGES_SUSPENDED in AudioService.
Send FOCUS_LOSS to any suspended app that is in the focus
  stack and remove it from the stack
Annotate nullability of package name, AudioAttributes
  and clientId for audio focus.

Bug: 119328282
Test: suspend app with focus, check output of dumpsys audio
Change-Id: I34103f8910146fc573c9efc806e8f1a1ffc722c9