Build micro and init variants of the container images

[lumarel]

There are still some TODOs left:

• Make sure that the UBI images are built very similar to the upstream images, and then removing the systemd install in the init container, related PRs are available here and here

If any changes/improvements are wanted, sure I can take them in account!
Testbuilds are available here: https://quay.io/repository/lumarel/rockylinux?tab=tags

[NeilHanlon]

lgtm

[NeilHanlon]

@lumarel do you want me to merge this and we can work on the other repo pushing (or maybe setting up syncing, instead?) later?

[lumarel]

@NeilHanlon I already had it planned out, now it is possible to create DOCKER_USERNAME, DOCKER_TOKEN, QUAY_USERNAME and QUAY_TOKEN, and easily push to them :)
And if we need more it's very easy to add.

Also Added a CI pipeline now for these images.

So yeah I think it's ready to merge, and when we are done with the changes in the kickstart repo and generated new images, we can also remove the systemd line in the init container, but that can be done later 👍🏻