MediaPlayer will now transition the background with color scheme

This change transitions the media player background whenever
the related color scheme has changed. Since the color scheme
is usually generated from the background, it should not trigger
superflous transitions.

Fixes: 246956968
Test: atest MediaControlPanelTest ColorSchemeTransitionTest
Change-Id: I963afcf4ba0fd8c2e9ebca4d634098f63454fab6