Avoid rebuilding the docker images on every CI run
We currently build the docker images in https://gitlab.com/tango-controls/cppTango/-/tree/main/ci for every CI run. This is a waste of CI minutes.
Instead we could:
- Move the docker files to a separate repo
- Build them their in CI and push to the gitlab registry of that repo
- Use the images here
This would also require us to version to the docker images so that we can test image updates.
Edited by Thomas Braun