Fluidsynth Engine: Implement a method for configuring custom CCs on every SF2 file.

[jofemodo]

Implement a mechanism on the Fluidsynth engine to configure custom CCs for every SF2 file.

Describe the solution you'd like

Ideally, autodetect the CCs supported by the soundfont

Describe alternatives you've considered

If not easy/feasible, we can use a YML file, as we already do on PureDate engine.

Additional context
A good example for testing is this SF2 file:

https://github.com/albedozero/fluidpatcher/blob/master/SquishBox/sf2/ModSynth_R1.sf2?raw=true