Update to latest mkosi
See the details but the TLDR is:
- our pinned version of mkosi could no longer build fedora because it couldn't find the f33 repos
- this was added to mkosi upstream a while ago but updating to latest mkosi broke debian/ubuntu with missing initrds
- this was now fixed mkosi upstream but debootstrap cannot handle Ubuntu 20.10 and later
- this is fixed here with forcing the same symlinks that have been in place for a decade now for every ubuntu version
Summary: we can now update ci-pipelines to latest fedora, ubuntu and debian.