rootston: Don't let the wlr_output handle the fullscreen view in case of layer-shell overlays

Otherwise the overlays will no tbe drawn.

Closes: #1300
(cherry picked from commit 175ccc25)
2 jobs for fixes in 1 minute and 7 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Build
passed build-with-xwayland #4660
librem5

00:01:03

passed build-without-xwayland #4661
librem5

00:01:07