docs(collector): add Kubernetes troubleshooting guidance

[MUSKANNISHAD]

This PR adds Kubernetes-specific troubleshooting guidance for the OpenTelemetry
Collector, including an example using kubectl debug with an ephemeral
container to diagnose networking and runtime issues.

Fixes #6129

[tiffany76]

Thanks, @MUSKANNISHAD!

@open-telemetry/collector-approvers and @atoulme, PTAL.

[dmathieu]

While this information can indeed be useful, it is also overly generic. Attaching onto a running container is far from being otel-specific.
So while this advice looks good, I'm not sure the otel doc is a good location.

[MUSKANNISHAD]

Thanks for the feedback! That makes sense.
I agree the technique itself is generic Kubernetes advice. My intention was to document how it can be applied specifically to troubleshooting OpenTelemetry Collector issues (e.g. exporter connectivity, DNS resolution for backends, or receiver port reachability).

I can update the section to make the OpenTelemetry-specific context clearer, or adjust the location if there’s a more appropriate place for this content. Happy to revise based on your preference.

[mx-psi]

I wonder if instead of adding that we can just add a link to https://kubernetes.io/docs/tasks/debug/debug-application/debug-running-pod/#ephemeral-container

I agree with @dmathieu that the info is overly generic, maybe adding that link is enough and we leave it to Kubernetes to document this