fix #25010: added midi generation for guitar bends

[alexpavlov96]

Resolves: #25010

changes that affect other things in midi export than only GuitarBend:

1. Duration of note with slide after grace note:
   el->push_back(NoteEvent(0, onTime, slideOn - onTime, velocity, !note->tieBack()));
   example:
   grace+slide.gp.zip

2. Resetting pitchwheel to 0 as close to next note as possible.

if (tick - specs.mStep > pwEvent->first) {
    tickForPwReset = tick - specs.mStep;
} else {
    tickForPwReset = (tick + pwEvent->first) / 2;
}

With new implementation of bends we have 2 notes (instead of 1), so we skip sound ON of second note (adding more pitchbends to keep sound on the needed pitch), so if pitchbend should be dropped as close as possible to next note - not to have sound artifacts

example:
bend+note.mscz.zip

[mikekirin]

I'm not 100% sure, but it seems NoteEvent m_len will always be 0 (slideOn-onTime). So this event makes no sense.

[alexpavlov96]

slideOn - time when slide should start, it's calculated from the end of the duration. See the file in description, there was bug, maybe I've also missed smth

[abariska]

1. Grace-bend should take its duration from previous not (not from the target one).
   In this case it should be part of A note. In properties of the grace-bend diagram should reproduce actual previous not (A), which allows to make the grace-bend note as long as we want.
   
   gracebend+bend+release.mscz.zip

2. Bend after prebend ends on one point earlier that it should.
   Last pitch change should be at the begin of the beat.
   
   prebend+bend.mscz.zip

3. Pitch of bends changes to less of pitch points (e.g. 8-9 for full bend instead of 10)

abariska.2024-10-10.at.18.08.21.mp4

4. 3 pitch points change instead 2 to be used for slight-bend.

[RomanPudashkin]

How exactly will this work if the bend starts from a tied note? Right now bends don't work at all during normal playback if they start from tied notes (#21345). So I'm wondering if we have the same problem with MIDI export...

[alexpavlov96]

any consequent combination of ties/bends is treated in 1 pass, and ignored if called again from another note of combination.
Rechecked, this combination also works. @abariska FYI

[abariska]

There're some minor issues but they will be reported separately