kcmaudiocd: Use flat QGroupBoxes, set documentMode on QTabWidgets, and remove excess padding
Makes it consistent with other KCMs and and Kirigami KCMs. This also adds ticks to sliders, and adds some vertical separators. The MR does this for all pages including plugins.
Only using one screenshot as an example - don't want to flood the page.
Before:
After:
Edited by Thomas Duckworth