Validate ComponentName for MediaButtonBroadcastReceiver

This is a security fix for b/270049379.

Bug: 270049379
Test: atest CtsMediaMiscTestCases
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:c573c83a2aa36ca022302f675d705518dd723a3c)
Merged-In: I4851eb506683c2666d57ec45bf9de787833d9636
Change-Id: I05626f7abf1efef86c9e01ee3f077d7177d7f662