Add Drumset checkbox to the Mixer
I think this have to be reconsidered. There are many issues related with the remove of this feature.
See: #31631: Cannot use SFZ and non-GM soundfonts on percussion instruments
#31646: Percussion clef cannot be assigned to a standard staff
#29401: Drumset entry in Mixer doesn't load sound from drums-only soundfont
#25982: [MusicXML Export] invalid MusicXML when instruments are missing from drumset