Rewrite the setup dialog

[Sawuare]

Changes:

This slightly modifies ConfigManager and its related files.

• Enhanced code quality and style.
• Commented some code.
• Improved translatable strings.
• Improved GUI and fixed minor GUI bugs.
• Improved the look for plugins embedding settings. 1c9ff9a
• Divided the MISC tab into 2 tabs: GUI and Projects, and moved some of its items.
• Moved some items to more appropriate sections.
• Changed the restart warning from a QMessageBox to a QLabel that is shown when a setting that requires restarting is changed.
• Removed the useless context help button. 8689e51

Closes #3681.

[lukas-w]

Screenshots by @Sawuare from Discord:

Edited, @Sawuare, removed the screenshots because they're out-of-date. Up-to-date screenshots are in the issue's description.

[michaelgregorius]

Don't know if this was already addressed in one of the commits but I wouldn't keep the option "Display restart warning after changing settings" where it is shown here:

Perhaps it can be moved into the GUI section because it affects the GUI behavior.

[tresf]

That pop-up needs to be abolished. We should reuse that same area to show a warning as soon as an item is clicked.

[Sawuare]

That pop-up needs to be abolished. We should reuse that same area to show a warning as soon as an item is clicked.

@tresf So you agree with the first comment in #3681?
If so, should that be done in this PR?

[tresf]

Yes, in principle, I agree.
This PR would be a good home.

[Sawuare]

I want the restartWarning label (see ded1765) to show when a setting that requires restarting is changed and hide when it's at its default (last saved) value, but I don't know how to implement that.
I already have a list of changes that require restarting and changes that don't.

Any help is appreciated. :)

Sorry for referencing the first issue in ded1765. 😅

[Reflexe]

A lot of changes are automatic and minor. That causes finding "real" changes much harder. Would it be OK if I'll modify this PR to include only major changes, without style and formatting changes?

[Sawuare]

@Reflexe Yes, please, but keep the order of statements as-is.

[Sawuare]

This PR is currently a mess with many stupid changes. I will hopefully tackle it next month and make it review-able.