Allow apps to provide custom Bundle equality logic

I'm having trouble with PlayerInterface.Listener.onTimelineChanged() not being consistently called when my SimpleBasePlayer-derived class updates an item's MediaMetadata.extra bundle and calls invalidateState().

I can see that this behavior is documented in various places:

• https://developer.android.com/reference/androidx/media3/common/MediaMetadata#extras()

  Given the complexities of checking the equality of two Bundle instances, the contents of these extras are not considered in the equals and hashCode implementation.

• https://developer.android.com/reference/androidx/media3/common/MediaMetadata#equals(java.lang.Object)

  Note: Equality checking does not consider extras.

• #470

I'm using the extras bundle to store information that changes at runtime (e.g. user-controlled tags), so I need some way to notify clients about changes. In order to force a playlist change when I modify the extras bundle, is my best bet changing the value of some arbitrary field in MediaMetadata, MediaItem, or SimpleBasePlayer.MediaItemData that I'm not currently using?