This change adds more standard metadata fields to Cast metadata including the artwork URL that makes the cast device show the artwork in the Cast route dialog (https://screenshot.googleplex.com/uj4n4Jqd7it9bob) and the Cast device.
This change also discriminates between media with an audio MIME type and others. For audio MIME type the Cast metadata is set to MEDIA_TYPE_MUSIC_TRACK which changes the layout and shows artwork and additional audio meta data to be displayed (https://screenshot.googleplex.com/ASy3KDcsTdJDM2T).
Issue: google/ExoPlayer#9663
PiperOrigin-RevId: 422589957
