Fix #24702: Voice too long corruption

[mathesoncalum]

Resolves: #24702

Introduced with #23911

The idea here is to scan backwards from the input position to find the previous ChordRest, check if the duration overlaps with the input position, shorten the previous ChordRest by the length of the overlap, and fill any remaining gaps with tied notes (if necessary).

This PR also addresses some janky input when switching voices in the middle of a tuplet (shown below) - for now we'll simply move the input cursor to the beginning of the tuplet. In future we may consider adding tuplets to the "new" voice in this case, but a few UX considerations will need to be resolved before we make this happen.

box-241001-1508-30.mp4

[cbjeukendrup]

It works well when the new duration of the previous note can be represented as a single duration, but otherwise still causes corruptions:

Schermopname.2024-09-28.om.01.54.24.mov

So changeCrLen is unable to split a note into multiple tied notes when it cannot be represented as a single note. There must be some other method somewhere in the engraving module that is able to do this, but I wouldn't know where.

[mathesoncalum]

@cbjeukendrup apparently it can actually split the note into multiple ties, but only if the target ChordRest is being lengthened instead of shortened... Looking into it.

[zacjansheski]

Tested on MacOS 14, Windows 11, Ubuntu 22.04.3. Approved
#24702 FIXED