[FruityPlug] Getting Channel Pitch Bend, Channel Volume, Channel Pan

- [ ] Channel Pan: Generators probably get this somehow
- [ ] Channel Level: Generators probably get this somehow.

- [ ] Channel Pitch
Synth do not seem to get it through any means.

The only thing approaching Channel Pitch Bend is to check this checkbox, then indeed the note pitch will be modified with the bend (but akwardly enough, we need to convert it back to MIDI where Pitch Bend is Channel-wise and not defined). Only MIDI 2.0 has per-note pitch bend. It's not clear how FL builtin generators apply Channel Pitch Bend, where they get it.

Start with the FruityPlug implementation and investigate how generators receive Channel Pan, Channel Level, and Channel Pitch Bend. Compare the available behavior with FL Studio's built-in generators; the work is done when these channel controls are reliably available to the synth and their expected behavior is documented or tested.

Written by the indexing model from the issue text.