Continuous MIDI recording

[riban-bw]

Is your feature request related to a problem? Please describe.
A user may play an excellent piece then not be able to reproduce it. Maybe they are interupted before recording or their attempts never quite recapture the original performance.

Describe the solution you'd like
MIDI recording should be running continually. The resulting files may be stored for a defined period of time (file rotation) or only stored if the user manually requests, e.g. in MIDI recorder, selecting current auto recording.

Describe alternatives you've considered
There could be an automatic pre-roll, i.e. prepending auto recorded MIDI to the start of a user triggered recording but this does not really capture what is required. There could be actions to push the pre-roll back by chunks, e.g. 5 mins, 10 mins, etc. but the user doesn't really know the exact timing they want.

Additional context
Chain outputs are all already routed to zynsmf. We could run a recorder in zynsmf continually with some form of auto file split (time / file size). We could switch from auto record to manual record and back when the MIDI recorder is manually started. Auto recorded files could be named / stored in an appropriate location, e.g. capture/auto_rec. MIDI files only take the space of recorded data, so silent files are (effectievely) empty and may be auto-deleted.