Fixes #6182 - Dynflowized repository update

- [x] Dynflowize repository update
- [x] Fix old tests
- [x] Make new tests
There was some async-part in the old orchestration as well https://github.com/Katello/katello/pull/4374/files#diff-f6aa9601a7c1afa89d06151a45d30777L78 - the generate_metadata triggers a delayed jobs task, so we would not be that far from the original orchestration.