OpulenZ refactor (attempt 2)

[yohannd1]

Continuation of #8314. Accidentally messed up the branch there.
This PR does some general refactoring of the OpulenZ code, trying to follow the modern guidelines. Other than that, there were some other changes as well:

• Use lambdas in favor of preprocessor macros (replacing MOD_CON, BUTTON_GEN, etc.);
• Add writeVoice method to simplify the syntax when writing to a voice's register;
• Move method descriptions to the header file;
• Refactor model & view structure to avoid duplication - added the OpulenzOperator{Models,Controls} classes (note: this change breaks translation strings!);
  • Small note: the op.1 knobs & buttons were exactly 90 pixels vertically away from the op.2 ones. That helped a lot here.

[yohannd1]

I believe I've finished this PR! I'll be testing this now, but so far I haven't seen any regression.