Removing a kernel zstream

Steps to do when support for a kernel stream has to be removed.

Background

Every once in a while, a RHEL stream reaches its end of life (EOL). In that case, CKI needs to update its setup to match this.

Steps to take

  1. Remove the zstream branches from the gitlab-ci-bot config.
  2. Remove the zstream tree from kpet-db. Also update the nvr tree mapping configuration accordingly.
  3. Remove the builder container image for it.
  4. Remove the container image from the .pipeline_images job template in the CKI GitLab CI/CD templates in cki-lib.
  5. Remove the container images from the gitlab.com and quay.io container registries. Check the Usage Logs tab to make sure the container images are really not in use anymore.