Add SystemAPI to override default media output switcher

To support RCN use case, allow system apps with the
MEDIA_CONTENT_CONTROL permission to declare that their MediaStyle notification
is for remote playback, and pass in their own device name, icon, and intent to
use in place of the default output switcher that appears on the media controls

Bug: 204910409
Test: atest
Test: manual with test app
Change-Id: Icbfa288c48da9c2ab2fdfdd6b0bfe2b545afaac0