Filter media controls by user

Adds a new step MediaDataFilter in the pipeline, after MediaDataCombineLatest,
which will only pass on media control loaded / removed events if they are for
the current user

If the user is switched, removes all existing controls for the old user and
then adds back any old controls for the new user

Fixes: 159958740
Test: atest com.android.systemui.media
Test: manual, switch users and observe controls updated correctly
Change-Id: Ia07180432df1ce031c42a6225d52160f83ef677e