Add docker image build and refactor template pipeline inclusion

Explicitly build minimal docker images that installs and runs python package.

Upgrade gitlab ci to work on instantiated version of the template rather then including {{cookiecutter...}/.gitlab-ci.yml directly as that can contain template arguments.

Override all template jobs on the trigger include to depend on the instantiated pipeline.

Profit

docker/ci-runner/Dockerfile

 FROM python:3.12
 
 RUN python -m pip install --upgrade pip
-RUN pip install --upgrade cookiecutter tox twine
+RUN python -m pip install --upgrade cookiecutter tox twine