[aurorae] Make QML-based decoration themes react to border size changes
Summary:
Currently only SVG-based decoration themes react to border size changes.
QML-based decoration themes on the other hand, for example Plastik, don't
react to such changes, only new windows will have decorations with the
new border size.
BUG: 408035
Reviewers: KWin
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D22665