Use compat framework to gate session actions

Adds CompatChange to check if an app posting media controls targets T,
and if so, that app's controls will use PlaybackState actions.
Otherwise, the notification actions will be used.

The MEDIA_SESSION_ACTIONS flag is set to false by default, and can be
used to override this and use session actions for all apps.

Fixes: 220034304
Test: atest com.android.systemui.media
Test: manual - verify in developer settings, override behavior works

Change-Id: Ie032fe9ec8ce7d46b1f9dc8f590ed6fbfa7ee9aa