CI: Bump to deb12, use latest image rather than pinning a hash.
To avoid images expiring simply depend on the latest deb12 image for now. Until we start to seriously record benchmark data pinning doesn't seem worth the trouble.
Due to a large amount of spam we do not allow new users to create repositories, they are "external" users. If you are a new user and want to create a repository, for example for forking GHC, open a new issue on ghc/ghc using the "get-verified" issue template
To avoid images expiring simply depend on the latest deb12 image for now. Until we start to seriously record benchmark data pinning doesn't seem worth the trouble.