Snap testing to stable blockers

Currently there are still some issues that block us from updating stable with KDE 6 and new GNOME.

• Plymouth black screen if kms not added to hooks in mkinitcpio.conf
• Manjaro M logo is not part of breath theming on a fresh install nor on upgrade for Plasma, see kde#2 (closed) -> not a blocker, can be fixed later
• Wayland selected by default on Plasma SDDM, needs to be switched back to X11, see kde#2 (closed)
• Breeze GTK theme in Plasma not applies after reboot, see kde#2 (closed) -> fixed upstream
• Install breeze5 for Qt5 application in Plasma 6, see kde#2 (closed)
• Plymouth for Nvidia without proper KMS setup
• breeze lockscreen upstream bug
• some vpau issue for Nvidia cards only in plasma profile -> only concerns Spectacle on Wayland, can be ignored for the snap
• Gnome zsh issue, so we have to check which Calamares is used and how the user is setup in configs there / Artem Grinev : did some quirks for zsh on plasma which might be missing on other editions
• Black screen on boot of live ISO and AMD with Plymouth -> issue with Plymouth 23/24, we stay on 22 for now was local config issue of the ISO, after adding Plymouth worked
• Don't install libva-vdpau-driver in new ISOs