[Flexiglass] avoid memory usage increase due to media notification spam

This CL applies the media notification spam prevention technique on
flexiglass.
It also applies the changes for drawables reuse flag on MediaActions.
This gives the chance for the drawables reuse flag to be applied on
legacy code. We can also limit the flag to only flexiglass if needed.

Flag: com.android.systemui.media_controls_drawables_reuse
Flag: com.android.systemui.media_load_metadata_via_media_data_loader
Bug: 360324938
Bug: 358402034
Test: atest MediaDataProcessorTest
Change-Id: I1abd7cb5b03200d66d6c77698f75f66e23fcb46d