AVRCP: Use MediaController

RemoteController has been depreciated since M.
MediaController lets us track a lot more things and update data as the
state of audio changes.

This also should fix some bugs related to metadata display not happening
on startup / track change / app change.

Bug: 27178384
Bug: 27745277
Bug: 26837775
Bug: 27534794
Bug: 27153373
Change-Id: I246d9641a5e921ed4434495f5c2dfac67d568952