Use PendingIntent for media click action over lockscreen

The clickIntent is provided by apps as the notification's contentIntent,
and it should be sent as is. This fixes the case where the intent called
an activity that could show over lockscreen.

Bug: 271845008
Test: atest MediaControlPanelTest
Test: manually with test app
(cherry picked from commit cb2904c7)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:223e9c5839308d8cd2e14242315a0e27a5154258)
Merged-In: I09d64452c46c4d21b9d958570020b2f5e6c2b23f
Change-Id: I09d64452c46c4d21b9d958570020b2f5e6c2b23f