Improve experience of publishing Features|Templates to Dockerhub

Reported in the [Dev Container Community Slack](https://github.com/orgs/devcontainers/discussions/3) [**(ref)**](https://github.slack.com/archives/C0431R35H37/p1680402927120119).

Dockerhub has a lot of special cases that this CLI's container registry implementation needs to support. One that I noticed is that the key name in the `~/.docker/config.json` is `"https://index.docker.io/v1/"`. This CLI currently uses this key to map to the published registry name - all other examples omit `https` and don't have any additional path (`v1`). Both of these components will need to be handled when building the URI

This could be lumped into https://github.com/devcontainers/cli/issues/468, as I think this is mostly an auth special case.

Once fixed, add regression testing to https://github.com/devcontainers/cli/blob/main/src/test/container-features/registryCompatibilityOCI.test.ts.