WSLc: Support non-docker style registries (e.g. Zot)

**Is your feature request related to a problem? Please describe.**
Currently WSLc is quite tailored towards `docker.io`. In particular, the authentication challenge follows the Docker client convention: It probes `/v2/` and expect that no authentication is required if the answer is `200 Ok`. However the OCI spec on image delivery [does not mandate this behaviour](https://github.com/opencontainers/distribution-spec/blob/main/spec.md#determining-support):

> This endpoint MAY be used for authentication/authorization purposes, but this is out of the purview of this specification.

**Describe the solution you'd like**

Implementing the [CNCF Distribution](https://distribution.github.io/distribution/spec/auth/token/) approach instead - try to authenticate lazily on first 401, *not* by probing `/v2/`. The question I haven't answered is how to detect login successful or not - currently `wslc login` always succeed when pointing at Zot / some compliant OCI registry. From a quick look, `podman` sends a query with `Basic` authz and deals with the response.

**Describe alternatives you've considered**

As a Zot registry user, I've raised a [separate feature request](https://github.com/project-zot/zot/issues/4224). Adding some `Docker-Client` might be good enough for my use-case (it'll trigger the workaround), but implementing the spec seems like a better direction.

Start by reading the OCI image delivery authentication guidance and the CNCF Distribution token-authentication approach referenced in the issue, then inspect the WSLc registry and `wslc login` entry points. Done means authentication is attempted lazily after a 401 rather than by probing `/v2/`, while login success or failure is correctly detected for compliant registries such as Zot.

Written by the indexing model from the issue text.