[Suggestion] Split OPM and OPN FM instruments editor

[freq-mod]

Was already suggested on Discord, obviously got lost in off-topic derailing, smh

Rationale for this is obvious: OPN and OPM FM are not the same. DT2, SSG-EG, advanced LFO, noise control.... it all confuses newcomers. Besides, we have a separate instrument type for VRC6 saw, OPLL FM, VERA vs other PSGs, etc...

[ZeroByteOrg]

If OPM gets its own Instrument editor, it would be nice if it were to have "preview-only" inputs for the LFO/Noise parameters just so you can play with it in an editor which is much easier than tweaking effect codes in the tracker itself and testing over and over. Obviously these parameters wouldn't actually be part of the instrument itself, so it could be confusing to newcomers who set these and then don't hear their effects in the music w/o using effect codes. :man_shrugging:

[tildearrow]

Also split NES and SN

[tildearrow]

How did I not mark this as done yet?