Pass gitlab projects' IDs through variables

Why is this change being made?

Extract hardcoded project id's to environment variables and set vars in CI. This allows to test it locally more easily without being afraid of accidentally breaking releases on the main project.

Also copied a bunch of stuff from gitlab to add support for rake specs.

If you want to test this locally, look for the changed markdown file in the diff, it has updated instructions on how to run this locally.

Part of POC: Add description from release post content ... (gitlab-org/gitlab#369032 - closed)

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

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