Allow screenOffScan to holders of MEDIA_CONTENT_CONTROL

Before this change, only holders of MEDIA_ROUTING_CONTROL are allowed to
perform screen off scans. But MEDIA_ROUTING_CONTROL is an appopp
permission that's not available to privileged apps via pre-granting.

MEDIA_CONTENT_CONTROL is a privileged permission that's pre-grantable.

Bug: b/352401364
Test: atest CtsMediaBetterTogetherTestCases CtsMediaHostTestCases
Flag: com.android.media.flags.enable_full_scan_with_media_content_control
Change-Id: I1118bf56a03977ddcfdf37c21f14f532ff3ad0d5