[nr-k8s-otel-collector] make collector observability resource attributes configurable

[achang209]

What this PR does / why we need it:

Exposes service::telemetry::resource as a configurable Helm value under collectorObservability.resource, allowing users to enrich internal otelcol_* metrics with custom resource attributes.

Without this, internal collector metrics arrive in New Relic with no cluster or environment context, making it impossible to distinguish which cluster or environment a collector's internal metrics originate from in multi-cluster deployments. The resource/newrelic processor correctly enriches pipeline metrics with k8s.cluster.name, but service::telemetry exports directly via OTLP and bypasses all pipeline processors, so it never receives that enrichment.

This PR adds a resource block under service::telemetry in both the daemonset and deployment configmaps. k8s.cluster.name is automatically populated from the existing newrelic.common.cluster helper, following the same pattern already used in the resource/newrelic processor. Additional arbitrary attributes can be passed via collectorObservability.resource for things like env.

This also fixes a minor inconsistency where values.yaml documented the scrape interval field as scrapeIntervalMs but the configmap template referenced it as scrapeIntervalSeconds.

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:

• The resource block is placed at service::telemetry::resource per the OTel collector internal telemetry docs, which applies resource attributes across all internal telemetry signals (metrics, logs, and traces)
• The resource block is only rendered when collectorObservability.enabled is true, so there is no impact to users who have not enabled collector observability
• k8s.cluster.name is always set automatically and does not need to be specified by the user
• The change is identical in both daemonset-configmap.yaml and deployment-configmap.yaml
• The scrapeIntervalMs → scrapeIntervalSeconds rename in values.yaml is a documentation fix only — the configmap template already used scrapeIntervalSeconds so behavior is unchanged

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 collectorObservability.resource to allow users to enrich internal collector metrics with custom resource attributes. k8s.cluster.name is automatically populated from the chart's cluster value, enabling multi-cluster observability out of the box. Additional attributes such as env can be passed via collectorObservability.resource.
• Fixed a documentation inconsistency where the scrape interval field was referenced as scrapeIntervalMs in values.yaml but scrapeIntervalSeconds in the configmap template.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[achang209]

@dbudziwojskiNR @Philip-R-Beckwith would love feedback on this at your earliest convenience. Thanks!