CI improvements
This MR updates CI config to be closer to the one in https://gitlab.gnome.org/GNOME/Initiatives/wikis/DevOps-with-Flatpak, and also cleans it up a bit
This MR updates CI config to be closer to the one in https://gitlab.gnome.org/GNOME/Initiatives/wikis/DevOps-with-Flatpak, and also cleans it up a bit