Draft: Add CI base image

Add use of a CI docker image containing all dependencies to pipeline, hosted at ichechestia/ci-base. This improves build times with the move to rocky8 as the dependency pull is much slower.

Ideally, this will support the future addition of images which have motr and phobos installed, allowing the CI to build against them and test these plugins.

Note, this image must be manually updated using the build scripts when dependencies change as due to runner config issues, we can't seem to authenticate with Docker in the CI pipeline. This, and the fact we do not have access to the gitlab internal image registry make this a non-standard workflow.

Closes #103 (closed)