When calling `MediaController.getCommandButtonForMediaItem(MediaItem)`
command buttons with custom commands that are not available
shouldn't be advertised to the controller when connected to
a Media3 session.
In contrast, when connected to a legacy session, available commands
are not enforced when advertising commands. Similarly, when sending
a custom commands that is referenced by a command button for media
items, sending is permitted without the command being available.
This is required because available commands match to custom actions
in `PlaybackStateCompat` of the legacy session. Adding commands for
media items to custom action of the `PlaybackStateCompat` would
interfere with other use cases.
Issue: androidx/media#1474
#cherrypick
PiperOrigin-RevId: 683717723
c4ff07e229