Replace packer with two custom shell scripts
Using actual VMs to build VMs is slow and error-prone (you need to use VNC to see what is going on, and booting takes over +110 seconds as we wait to be sure Arch Linux is ready). build.sh can build all three images in ~135 seconds (assuming all the packages is cached), we still need to use a VM for the actually building in GitLab CI (as that is the only safe way it can be done at the moment), which is a bit slower (~22 min vs ~13 min (Packer)), but that isn't really a big issue. In the future we can hopefully switch to Kate Containers and reduce the build time significantly.  https://gitlab.archlinux.org/archlinux/infrastructure/-/issues/108
It is getting late, so I haven't got time to test the whole script (
create_image isn't tested). It lacks the vagrant images and the box creating logic (probably +100 lines with some inlining).