Call listeners whenever players are removed

AudioPlayerStateMonitor.onAudioPlayerStateChanged isn't called all the
time when players are removed. This change makes the listener be
called whenever players are removed.

Bug: 68733075
Test: manual tests for restoring media routes and handling media keys
Test: same result from Media CTS with and w/o this change
Change-Id: I7219d757a7001b83e03c8d04fc1cabb12638dafa