Support multiple docker registries

[Dav1dde]

Currently craft always assumes dockerhub when using the docker target. Ideally we can have multiple docker targets targeting different registries, like Github's GHCR or Google's Artifact Registry.

For this we either need more targets or extend support for the existing docker target to support multiple registries and credentials for these registries.

[aldy505]

Just saw this. Let me know if you need help @BYK

[aldy505]

@asottile-sentry I just heard from Burak, we can have a separate discussion here about what to do with Craft moving forward.