FR: add multi-device MIDI output to global clock

[dndrks]

from https://llllllll.co/t/norns-clock/30738/104

currently, users can only send MIDI clock from the global clock to a single output. this is fine if folks are working with devices which can be daisy-chained, but more and more gear is made with USB-MIDI only which makes passing clock through multiple devices difficult/impossible.

it could be useful to offer this sort of multing inside of norns itself, perhaps as a context menu inside similar to SYSTEM > DEVICES > MIDI, where many devices can be specified as recipients of MIDI clock out. to avoid introducing a nested menu inside of a nested menu (introducing a new menu paradigm), this could maybe manifest as a list of ports (1-16) with simple "yes/no" toggles.

[tehn]

we should have a discussion re: SYSTEM DEVICES 3.0 update, which should have per-device config. we could add some clock args here.