Kairos dockerfiles should create full kairos images

[jimmykarily]

Currently, we build the Dockerfiles, and then we do many more things in Earthly.

All this logic can be moved to the Dockerfiles. This will allow the creation of other derivatives without any Earthly knowledge.

Items extracted from TODOs (#1912):

• Merge Alma, Rocky and Fedora to one family Dockerfile
• Move rest of logic from Earthfile to Dockerfiles
• Create a reusable workflow that simply calls docker build, passing the required build-args
• Delete the earthly base-image target and force the use of the above workflow anywhere needed
• Make all remaining earthly targets to use a pre-cooked KAIROS_IMAGE rather than calling +base-image

[jimmykarily]

Better merge this first: #1939

[mauromorales]

I will better not merge since it makes it less explicit for some of the actions in which distro they should be run and in which not