[CI] Stop using images for git-based CI jobs

The images containing nighly builds of the current development branch of the core and staging modules are no longer up-to-date, because they are no longer updated automatically. One cannot even update them manually by triggering a pipeline. The only possibility is to build them locally and push them to the registry manually.

This is not a viable workflow to me. Hence we switch to building all dependencies in this case. Once there are nighly build images again, we can revert the change if we think it takes up to much resources.