MessageBoxes in Creator have ugly, crumbly icons

Replacing QTCREATORBUG-22132 because the icon described there was removed because of this issue.

1. Have a HiDPI screen running with screen scaling.
   I have it set to 150%.
2. Start Creator with empty settings.
3. Go to "Tools" -> "Options..." -> "Environment" -> "Interface".
4. Select a different language from the combo box.
5. Click "OK".
   You'll see something like this:
   

The icons should be smoothly scaled instead.