Inflate media notification icons in MediaCoordinator

In the old pipeline, notifications were inflated before the media
notification(s) were filtered out and used to populate the quick
settings, lockscreen, or AOD media views.

In the new pipeline, MediaCoordinator filters out media notifications
before PreparationCoordinator inflates them, so they're never inflated.

This is mostly okay, except that the AOD (and maybe lockscreen?) media
views use one of the media notification's icons to label the media
metadata, and that icon was no longer getting inflated.

Therefore, have MediaCoordinator do the necessary subset of the work of
PreparationCoordinator for the media notifications it filters out:
create and update icons for notifications it filters out, report
inflation errors back to StatusBarService, and do the bookkeeping
necessary to do the right thing (create, update, or nothing) each time
we see a notification.

Bug: 228397680
Test: atest MediaCoordinatorTest (added some test cases)
Change-Id: Ic42c276e5a973cdd260a8c4729a5abdf53987199