This fixes older releases not appearing in the changelog.

Refactor three scripts into one in order to support triggering a new
pipeline in the case of a skipped MR pipeline. This was not possible to
implement with the previous three-script design. The single scripts
were not used in other places anyway.

The dynamic job was only necessary because GitLab did not expand
variables in the "trigger:project" keyword:
https://gitlab.com/gitlab-org/gitlab/-/issues/347469

This has been fixed in GitLab 15.3, so we don't need it anymore:
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/92346

Everytime we push a new commit to a branch, a new pipeline is created.
Often the pipeline for the previous commit has not finished yet, and
GitLab does not automatically cancel it. It consumes valuable build
time, even if we don't need the results anymore.
Adding a MR pipeline job to search for previous pipelines on the same
branch and cancel them explicitly.

For a given project all artifacts may be deleted. This was needed due to
space limitations on the gitlab server.

Otherwise the parent pipeline is stuck in "running" state until the
manual action has been performed. See for reference:
https://gitlab.com/gitlab-org/gitlab/-/issues/361574

The script has mostly been copied from alphaplan_fwr.py, but with
different input data.

Adding a job to the CI-test environment for testing this.

This script has mostly been copied from alphaplan_fwr.py, but with
different input data (artifacts from the SoftwareStore deploy job) and
without actually importing the data to the Alphaplan database.

Adding a job to the CI-test environment for testing this.

Rename all stages to uppercase on this occasion, since we're adding
stages with names containing multiple words.

isort is a Python utility to sort imports alphabetically, and
automatically separated into sections and by type.

Instead of copying a packaged release from the SoftwareStore, download
artifacts from an actual build job.