Add the "client-secure" Pod to the Helm chart?

**Is your feature request related to a problem? Please describe.**
It would be nice to have an easy way to connect to the CRDB cluster in a Kubernetes cluster.

**Describe the solution you'd like**
The docs even note this as a thing you might want to do, and link you to the almost ready-made example of how to create a pod to do that: https://github.com/cockroachdb/cockroach/blob/master/cloud/kubernetes/client-secure.yaml

Can that just make its way into the Helm chart? (It would be fine, and perhaps preferable, if that was being a `values.yaml` flag to enable/disable it, too.)

I'd also switch this from a raw `Pod` (which isn't recommended, and has various downsides) to a `Deployment`¹ with `replicas: 1`. `sleep` (at least the one that is in GNU coreutils) can be invoked as `sleep infinity`, and `dumb-init` will all the pod to shutdown gracefully; a minimal "do nothing" pod is `dumb-init -- sleep infinity`, and then you don't need the `terminationGradePeriod` directive.

**Describe alternatives you've considered**

The status quo, of having it as an example:
* Since one already is using the Helm chart, it's harder to pull in than just "enable this flag".
* Orgs like mine want to vendor upstream software, and other orgs want to understand when & where 3rd-party code is. Random files like this — where I pull in this file, make a bunch of changes — make that very muddy, and don't integrate well with existing processes. But we have a process to vendor a Helm chart: so it if just gets packaged with that, then :rocket:

**Additional context**
¹This does have the downside of making the pod name ugly. A `StatefulSet` would make the pod name nicer, unless there's some magic way with a `Deployment` to do nice names that I don't know about.

Jira issue: CRDB-36686

Jira issue: HELM-44