ci: upgrade and pin to ubuntu-22.04 project-wide for CI runner images

[petermetz]

1. This does not upgrade all the container images that we build and publish
   as part of the project, it just upgrades the runner images that are being
   used by the continuous integration environment.
2. I also deleted a .yaml file that I left in the diff of another pull request
   by accident. Apologies for the littering.
3. Upgrade: as-in, I bumped the 20.04 versions to 22.04
4. Pin: as-in, replaced ubuntu-latest with ubuntu-22.04 everywhere.
5. Reasoning: 24.04 is out now and so we have to keep up with the times
   because soon there'll be a stop to security patches even on what used to
   be LTS (20.04). It is better to find out now if we have a problem with
   ubuntu 22.04 rather than later when it's become urgent to upgrade.
6. The risk of something breaking because of these upgrades is most likely
   low since ubuntu is one of the most stable distributions out there.

Signed-off-by: Peter Somogyvari [email protected]

Pull Request Requirements

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A Must Read for Beginners
For rebasing and squashing, here's a must read guide for beginners.