Add the MediaPlayerList and fix some checks

The MediaPlayerList class handles keeping track of all the Browsers and
Media Controllers. It will also keep track of which is the active
controller and be able to return the most current metadata.

Fix the metadata equals check as it was comparing more than we wanted.
Depending on where you retrieve the information certain fields may be
filled out differenty even though the song represented was the same.

Also add a queue ID check for the MediaPlayerWrapper in addition to a
null queue.

Bug: 68854188
Test: Compile and Manual testing on full build
Change-Id: I1a25f5a44eb2b5b1775c04baefbfc66c018251e9