Allow dask cluster port forwarding directly

This is just a quick idea, not sure if it is actually possible.

In the operator docs we have a code example for port forwarding a cluster.

```console
$ kubectl port-forward svc/simple-cluster 8786:8786
```

The service is created by the operator, so the user may not necessarily know it exists and will have to discover it either by querying the API or reading the docs.

I wonder how much work it would be to enable something like

```console
$ kubectl port-forward daskcluster/foo-cluster 8786:8786
```

This way the user would be port forwarding the resource they created which might make more sense to them.

_I also wonder if it would be possible for ingresses to point to `daskcluster` resources instead of services._