Add shuffle functionality to Carpeggio to mix up notes on the grid

[benirose]

This was a feature I added on my fork and people seemed pretty excited about it when I shared it on Reddit, so I wanted to open a PR to the main repo to offer it back to you. It seems to just barely fit!

It allows for shuffling the grid in Carpeggio via a new on-screen parameter. It is disabled by default and changing chords disables it as well. When turning the encoder towards shuffle, it will swap a bunch of notes around, creating new melodies. Further turns to the right will continue to shuffle the grid. Turning left back to "play" mode will re-imprint the chord in its normal ordering.

The only shortcoming of this feature is that it doesn't save the shuffled grid to memory. Even if I kept track of the index movements so we could rebuild it on load, I couldn't think of a way to fit that in the remaining 16bits of Pack data.

You can see it in action on the Reddit thread I shared it in, as well as the enthusiasm from other o_C users: https://www.reddit.com/r/modular/comments/r6e0wd/been_tinkering_with_my_own_fork_of_hemisphere/