Unify docker images

Basically drop the runtime images and the split.

This is meant to replace both the runtime and build images. Spliting it in two increasing the maintainance required without any big benefits.

Additionally somewhat restructure the docker direcotry. The idea is that now each image will have its own context dir.

example:

tree docker/fedora/
docker/fedora/
├── cleanup.sh
├── Dockerfile
└── prepare.sh