gitlab-ci.yml: use new jobs from the manifest repo
The .workspace and .build-docs allow simplification of the two similar jobs present into this repository. The .workspace job completely replaces the local copy, with a single configuration variable to enable testing of incoming changes.
The build job becomes build-docs and extends both the .workspace job and the .build-docs job, reusing both the scripts to perform everything that was formerly specified explicitly.
The deploy job now extends the .workspace job but is otherwise unchanged.
Signed-off-by: Zygmunt Krynicki email@example.com