Polyphonic aftertouch + Last note aftertouch

[probonopd]

Reference:

• https://github.com/probonopd/MiniDexed/discussions/162

We currently have monophnic (channel) aftertouch. The next big step would be polphonic aftertouch. Also, we might want to implement "last note aftertouch", in which monophonic (but not polyphonic) aftertouch capable MIDI controllers would control the last pressed note only. It should be a configuration setting whether monophonic aftertouch should affect all notes (as it is now) or only the last note.

Idea credits: youtube.com/watch?v=eg6X9fQ-U4s