kcms/fonts: warn if trying to use a "Display" font
Reason for the change
These fonts are not actually intended for use on computer screens, but the word "display" seems to cause people to make the opposite assumption. As a result, there's a constant trickle of bug reports and complaints about weird text when using one of these fonts.
Add a warning in the KCM so people learn the truth.
Test plan
- Open the Fonts KCM
- Change a font to something with "Display" in the name
Screenshots or screen recordings
Bugs fixed
N/A
Also includes
Two bonus commits:
- One small UI improvement to make another warning message using the Warning InlineMessage type
- Another commit to refactor two InlineMessage visibility conditions