DO NOT MERGE Add test for system gallery storage permission as system fixed

Due to the WRITE_MEDIA_IMAGES app op, photos access cannot actually be
denied. Since the role is fixed, the permission effectively is, too. This change
adds tests for this.

Bug: 315320090
Merged-In: I77e68ff55aa11f21c54517369771375f6234cfc1
Change-Id: I77e68ff55aa11f21c54517369771375f6234cfc1
Test: atest MediaPermissionTest#testGalleryAppListedAsFixed