Improve ECK diagnostic collection

Raising this on behalf of a customer.

> Needing to generate diagnostics file for the cluster was found to be painful.
>
> I had to build and test my own version of a wrapper script around this diagnostics script to attempt to generate a diagnostics on a kubernetes ES pod for which we didn't have an external service for (in other words, no addressable domain from which we could access elasticsearch by an app outside of kubernetes).
>
> I was eventually about to get something working with a variety of kubectl commands although I feel this should have been much easier to accomplish.
>
> A new member of our Observability team has had to run a diagnostic recently using v8.2.2 of the package (I was previously using 7.1.5) and unfortunately that version does not work with my helper script.
>
> Any idea what kind of time line we could expect until we have something available for this?

Code for the wrapper script is [here](https://gist.github.com/hartfordfive/27a80b3311e1d7efc84dbad31d2bfbc1) - note it currently only works against 7.1.5 of the ECK diagnostics script.