This will make the manifest project support the "skip build" label.

This reverts commit 4db257d3.

It does not work on the manifest, because we do not run merge request
pipelines there, so CI_MERGE_REQUEST_LABELS is not set at all.

GitLab API has changed:
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/94164/diffs#diff-content-c201dae00b72426693ddcb40edf6005e7702e935

Instead of hard-coding the project list in the changelog generator
script, make them passable via arguments. This way we can have different
changelogs in different envrionments. Hence we're adding the changelog
job in the ci-test environment as well.

This case should trigger a new pipeline instead of reporting an error.

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.