Allow mediaserver to access vendor_app_file

Currently, when vendor APK try to use MediaPlayer to play its audio
resource, it would fail due to this neverallow rules.

avc: denied { read } for path="/vendor/app/TicFitness/TicFitness.apk" dev="dm-1" ino=183 scontext=u:r:mediaserver:s0 tcontext=u:object_r:vendor_app_file:s0 tclass=file permissive=0

Bug: 78436043
Change-Id: Id910184c16955f9e4e4c8d3bb6eca2253ab59063