[nr-k8s-otel-collector] Adding ksmSelector for prometheus receiver

[tviaud]

Is this a new chart

No

What this PR does / why we need it:

This pull request adds support for customising which kube-state-metrics instance is targeted by the Prometheus receiver in the otel deployment. This is useful for clusters running multiple kube-state-metrics instances, allowing users to specify a label selector to avoid scraping duplicate metrics.

This is mostly mirroring what's done for the ksm component in the newrelic-infrastructure chart: https://github.com/newrelic/nri-kubernetes/blob/main/charts/newrelic-infrastructure/values.yaml#L255.

This would be useful in migration cases to keep nri-bundle and nr-k8s-otel-collector up at the same time for example.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• Chart Version bumped
• Variables are documented in the README.md
• Title of the PR starts with chart name (e.g. [mychartname])

Release Notes to Publish (nr-k8s-otel-collector)

If this PR contains changes in nr-k8s-otel-collector, please complete the following section. All other charts should ignore this section.

🚀 What's Changed

• Added configurable label selector for kube-state-metrics discovery via receivers.prometheus.ksmSelector to prevent duplicate metric scraping when running multiple kube-state-metrics instances in the same cluster (e.g., during migration from nri-bundle to nr-k8s-otel-collector).

[dbudziwojskiNR]

@tviaud, thanks for the PR! This looks great. Just left a few comments and we can work to get this merged. Thank you!