Add MediaBrowserImpl

This class implements the media browser service interface as a standalone class for clearer separation of concerns (otherwise everything would need to go in PlayerService, since PlayerService overrides MediaBrowserServiceCompat)

Co-authored-by: Haggai Eran <haggai.eran@gmail.com>
Co-authored-by: Profpatsch <mail@profpatsch.de>

Author: 3 people