cicd: rules:changes logic does not support variables
GitLab sucks in this regard, we will have to workaround by using yaml anchors or other "basic" yaml features to achieve at least somewhat reduced job definitions. The current variable-based approach may end up working in the future, see:
- https://gitlab.com/gitlab-org/gitlab/issues/34272
- https://gitlab.com/gitlab-org/gitlab/issues/8177
- https://gitlab.com/gitlab-org/gitlab-runner/issues/1809
For now, fix using yaml anchors or similar.