Fix microtuning warning from widening instruments

[rubiefawn]

Resolves #7798.

The culprit was the little text warning under the instrument tuning view informing the user that MIDI-based instruments do not support the microtuner. The entire instrument window was expanding horizontally to accommodate this. The "fixed size" of the instrument itself has no bearing on the other tabs in the instrument window, it seems.

This PR solves this problem the same way it was solved in d447cb0: the text has received a fixed maximum width. This is a bit of a hack, but there are no instruments that are or can be resized to larger than 250px that are MIDI-based. A cleaner possible solution would be to refactor things so the other tabs have their width determined by the instrument size, but this works for now.

[JohannesLorenz]

I tested the PR and it works and the code is correct.

but there are no instruments that are or can be resized to larger than 250px that are MIDI-based

That's right for now, but with #7201 going to master (hopefully soon), many Lv2 instruments can be resized larger than 250px - if we allow Lv2 UI to be displayed inside the InstrumentTrackWindow (vs in a new popup window).

If "instrument windows [...] have their width determined by the instrument itself" (quoting you from Discord, btw this is the same solution I proposed in #7524 which I withdrew in favor of #3532), this PR might be restricting the size unwanted.

[regulus79]

WHOAH YOU ACTUALLY FOUND IT?! Congratulations, I could not figure it out!!! 🎉
I briefly tested it, and it's definitely fixed!

[sakertooth]

This PR solves this problem the same way it was solved in d447cb0: the text has received a fixed maximum width. This is a bit of a hack, but there are no instruments that are or can be resized to larger than 250px that are MIDI-based. A cleaner possible solution would be to refactor things so the other tabs have their width determined by the instrument size, but this works for now.

Maybe we can explain some of this in a TODO comment, but LGTM overall

[rubiefawn]

WHOAH YOU ACTUALLY FOUND IT?! Congratulations, I could not figure it out!!! 🎉 I briefly tested it, and it's definitely fixed!

Hmmm, in the images you shared I am still seeing ~3px of extra space on the right that shouldn't be there. It's much less noticeable than the previous gap, but it looks like the problem isn't fully solved. It may be that the problem is better or worse for any given user depending on the system UI font, which explains why I don't see that gap on my machine. I'll take a closer look.

Edit: Sanity check, I cannot replicate this on 1.2.2 stable, nor the current 1.3.0-alpha, so whatever is causing it happened since then.

[he29-net]

Just for more information, this is how it normally looks like:

I.e. the text is supposed to simply wrap around automatically, without forcing the parent to grow wider. From the screen shots I can see that it is the classic Qt issue that I've been running into for years: everything is scaled up by some factor, say 1.5x if you have fractional scaling enabled, and then, some text is scaled up by 1.5x again. You can also see it in your VeSTige screenshot: the "Show/Hide GUI" and "Turn off all notes" button labels are larger than they are supposed to be. For comparison:

AFAIK this affects all standard Qt widgets (buttons, labels, ..). LMMS fixed-size widgets seem to be unaffected (possibly because they have fixed font sizes specified in pixels?) Not sure how to fix that "properly" for all the widgets, or if it is even possible. Qt DPI scaling support is just.. fun...