Fix multimonitor blur
Summary:
On wayland blur on secondary monitor would not render correctly.
BUG: 393723
Depends on D12452
Test Plan:
- use more than one output
- log in in a wayland session
- open a transparent window (for example: Konsole with transparent and blur enabled profile)
- drag the window to another screen
- blurs the content under the window corretly
Reviewers: KWin, graesslin, davidedmundson
Reviewed By: KWin, davidedmundson
Subscribers: apol, zzag, davidedmundson, kwin, KWin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D12678