Github client uses releases rather than packages for user repositories

[ribbybibby]

The Github client implementation seems to use releases to infer tags for Github packages at the user scope. It may be the case that release tags and tags in a ghcr repo align, but that is not necessarily the case.

I think we should be using the Packages API rather than the Releases API.

https://docs.github.com/en/rest/packages/packages?apiVersion=2022-11-28#list-packages-for-a-user