[Styles KCM] Port away from QDBusInterface
Check GTK module being loaded asynchronously and load the page and its associated model only when entering the GTK subpage.
-
GTK config button still shoen here
-
GTK model still loaded properly
-
changing GTK themes still works
-
the page reflects the current GTK theme
-
preview is broken but that was before, too, I don't have a
gtk_preview
app in my system andgtk3_preview
just crashes when I try to run it