[Epic] Deprecate openedx.yaml and move to catalog-info.yaml

[feanil]

See this conversation for more details: https://github.com/openedx/open-edx-proposals/pull/343/files#r900223439

Summary

We decided to start using backstage for tracking maintainership. This means there is now both a catalog-info.yaml file and an openedx.yaml file at the top level of repos. Many of the goals of the openedx.yaml are fulfilled by the new catalog-info.yaml file. Once the backstage deployment has been running for a while and we're confident that we're going to be moving in this direction, we should go back and migrate the last of the things from the openedx.yaml file.