sudo x11-app does not work with Wayland session, works fine with "GNOME on Xorg" session

sudo x11-app, e.g. sudo gvim /etc/some-file, currently fails when running a Wayland sessions where as doing this under a "GNOME on Xorg" session works fine. From the user pov this is a clear regression and a reason to stick with X11 which is not what we want.

As Olivier Fourdan mentions here: https://bugzilla.redhat.com/show_bug.cgi?id=1274451#c2 this can easily be fixed by passing an xauth file to Xwayland when mutter starts it. Just like gdm and startx pass a xauth file to Xorg when they start Xorg.

Note this problem is also reported in various other places: https://askubuntu.com/questions/961967/why-dont-gksu-gksudo-or-launching-a-graphical-application-with-sudo-work-with-w https://bugzilla.redhat.com/show_bug.cgi?id=1274451 https://bugzilla.redhat.com/show_bug.cgi?id=1266771 https://bugzilla.redhat.com/show_bug.cgi?id=1266792 https://bugzilla.redhat.com/show_bug.cgi?id=1274634