SDK / exoplayer

- This is for consistency with PlayerControlView.

- Also update PlayerNotificationManager notification if shuffle
  mode changes. This is for consistency with what happens when
  the repeat mode changes. By default the notification will be
  unchanged, but custom implementations can extend and then
  override createNotification, and given these modes change
  infrequently it feels like we can just do this. The alternative
  for achieving consistency would be to remove handling of repeat
  mode changes.

Issue: #6582
PiperOrigin-RevId: 277925094