Merge the hackathon branch and PRs

[Lorak-mmk]

All the work during the internal hackathon was done on branch-hackathon.
There are still many hackathon open PRs. We should get all of that into main.
Plan:

• Extract ccm integration from the hackathon branch
• If any open PRs do any changes to this integration, cherry-pick those changes
• Make the necessary modifications. One I know is that we should not actually make a separate folder, but a subfolder in integration tests. This way there is no problem with sharing test utils, but we can still guard ccm tests with a cfg
• Open a PR with above integration, and work on it so we have something satisfactory (because now we don't have to do this in a rush before hackathon).
• After merging it, adjust and merge stuff that is already in branch-hackathon.
• Take over open unfisnished PRs - or work with the original authors, whatever is easier - and merge them.

Putting it in milestone 1.4, because it will take some time, but we should not wait with working on it.