Improve CI/CD Pipeline speed

Hey there! While working on the Diátaxis !2988 (merged) MR I noticed some chances for speed improvement on the overall pipeline.

  • cue is installed 5 times
  • crdoc installed 2 times
  • wheel is installed 7 times
  • additional python installs needed for pipeline only: falke8, mypy, nose2, coverage, sphinx>=4.0.1 sphinx-rtd-theme snowballstemmer'<'3
  • additional apt installs needed for pipeline only: graphviz (installed 2 times atm)

So I would propose the following steps to fix this:

  • move dependencies from requirements-build.txt to setup.py via extra_require (see SOF) and install pip3 install -e .[dev]
  • provide development Dockerfile installing all development dependencies
  • add new job to build the development docker image on stage management_prepare and rule watching for changes to setup.py
  • adjust jobs using "${CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX}/python:${PYTHON_IMAGE_VERSION}" to new dev image