Font scaling issues

[FliegendeWurst]

Tracking issue for all font scaling bugs.

Description

Changing the global font factor produces some weird artifacts.

• [ ] Icon size does not adapt
• [ ] Settings tree (left panel) is always 16pt
• [ ] Icons in proof tree are always scaled to the previous setting of the factor (hard to fix)
• [ ] #1643
• [ ] Tickmarks for Max. Rule Applications stay the same
• [ ] Bookmarks stay the same (PR pending)
• [ ] Report feedback: doesn't scale
• [ ] Proof Management: checker dialog is too small
• [ ] Proof Management: selection dialog buttons too small (PR pending)