panel: Fix quicksetting delegate width not getting enforced on label

Devin Linrequested to merge
work/fix-elide into master

Fix https://invent.kde.org/plasma/plasma-phone-components/-/issues/116 by enforcing max width on label, and ensuring it elides.

We do need a scrolling text component so that users can read the elided text, but that's too big for the scope of this.

Needs to be cherry picked to 5.23

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