Provide a way to sign collections for Red Hat certified and supported collections as well as Private collections in Private hub.

 Planning: https://hackmd.io/BDVDUcOEQgqCHr4nUWcXUQ

Main PR: https://github.com/pulp/pulp_ansible/issues/757

Old/Duplicate Pulp Issues:

https://pulp.plan.io/issues/9543

https://pulp.plan.io/issues/9544

https://pulp.plan.io/issues/9545

https://pulp.plan.io/issues/9546

PRD (same as in feature linked here)

https://docs.google.com/document/d/1aGiEaYtQXa8H80zdHr-Fa3JXisCsN3xPH9HcHREmdCg/edit?usp=sharing

Architecture Spec

https://docs.google.com/document/d/1o5gJUuY-bpNfYNMchXe0u3pohMNYxrACRtJRcngw7Lk/edit