Multi-arch support for OCI-repo

[frelon]

This issue is about being able to build and push multi-arch images to the same repo, instead of having to use different OCI-repos based on arch.

Was looking into this a bit on hackweek and building and pushing multi-arch packages required very small changes.

The bigger problem seems to be saving the repository metadata when doing luet create-repo and consuming that based on the client arch.

Adding this issue to keep a trail of what was tried and if anyone else finds it interesting.

WIP branch here: https://github.com/frelon/luet/tree/image-ref-change
and a package repo: https://github.com/frelon/packages

[mudler]

That's awesome and looking great! Thanks you so much! care to open up a PR to see if it's passing tests?