SDK / exoplayer

If the service ever has been started but is not in the foreground, the
service would be terminated without calling onDestroy(). This is because
when onStartCommand returns START_STICKY [1], the app takes the
responsibility to stop the service.

Note that this change interrupts the user journey when paused, because the
notification is removed. Apps can implement playback resumption [2] to give
the user an option to resume playback after the service has been terminated.

[1] https://developer.android.com/reference/android/app/Service#START_STICKY
[2] https://developer.android.com/guide/topics/media/media-controls#supporting_playback_resumption

Issue: androidx/media#175
#minor-release
PiperOrigin-RevId: 492192690
(cherry picked from commit 6a5ac191)