Implement ADR12: Cluster Wide Resources

[malexmave]

This story tracks the implementation of ADR-0012, which specifies the concept of cluster-wide resources (which I'll abbreviate CWRs here).

TODOs (incomplete list, feel free to add additional points):

• [ ] Come to a final decision on which variant of the ADR we will implement
• [ ] Create new CRDs for CWR types, as specified in the ADR
• [ ] Implement support in the operator
• [ ] Decide if we want to switch to CWRs by default for the autodiscovery (I would argue yes). If so, update the autodiscovery implementation
• [ ] Add unit and integration tests
• [ ] Double-check that K8s RBAC protects these resources in the way we expect it to
• [ ] Update the documentation with information on how to use CWRs
• [ ] Update autodiscovery documentation
• [ ] Update UPGRADING.md, since this will be a breaking change
• [ ] Optional: Write a blog post
• [ ] ... Probably more