MediaSession2: Add MediaPlaylistController.PlaylistEventCallback

This includes following changes per offline discussion
  - Add MediaPlaylistController.PlaylistEventCallback
  - Add following APIs to the MediaPlaylistController
    * registerPlaylistControllerCallback() /
      unregisterPlaylistControllerCallback()
    * getRepeatMode() / setRepeatMode()
    * getShuffleMode() / setShuffleMode()
    * setPlaylist() with metadata
    * setPlaylistMetadata() / getPlaylistMetadata()
  - Add following APIs to the SessionCallback
    * onMediaPrepared()
    * onPlayerStateChanged()
    * onBufferingStateChanged()
  - Remove following methods from ControllerCallback
    * onPlaylistChanged()

Bug: 64098437
Bug: 74157064
Test: passed MediaComponentTest
Change-Id: I5ad12a9a5d6a7d9e23a577dca8ea26fbacb8f259