Test merge 818 828

[Photon89]

@DarthGandalf @underwaterdba

I tried to resolve the conflicts between #818 and #828. Cannot do any multimonitor testing though.

[Photon89]

So, now, according to my testing, the current state supports both the redo from #828 and the xdg-portal targets from #818. I cannot test whether multimonitor capture works as expected though. A new $screen_mode variable, which has been initially introduced by AI while trying to solve the merge conflict, is supposed to tell whether we are talking to the current monitor or not (defined in line 6337). It is passed to Wayland::xdg_portal but not used there. I cannot tell if it is useful because of lacking testing on multimonitor...