AVRCP: Workaround Queue ID & metadata updates

When a player with a queue updates their track, it comes in two separate
parts from MediaController.Callback:
 - Queue ID is in onPlaybackStateChanged
 - Metadata is in onMetadataChanged

Because the ordering of these two is not specific, both must change
before we have a consistent data state to present the carkit if the
Media client has a queue.

Even though the only thing sent in the Track Changed notification is the
Queue ID, the request for metadata often comes before the Metadata has
been updated after that notification.

Refactor Track Changed notification to keep track of the last data we
sent to the controller, and send new tracks when both Queue ID and
Metadata have changed.

Test: various carkit testing with track skipping
Bug: 37707672
Change-Id: Ibf9f725f6912955a65421786068921489dbf8e45
(cherry picked from commit 5aca05c1)