[k8scluster] Document which metrics allocatable_types_to_report setting produce

[ChrsMark]

Component(s)

receiver/k8scluster

Describe the issue you're reporting

There are some node allocatable metrics of the k8scluster receiver that are enabled through the allocatable_types_to_report setting. However, it's not clear from the docs what are the names of the metrics, so this might be confusing for users. We need to explicitly list the metrics in the section of this setting.

(These metrics are not part of the metadata.yaml file yet, cause they are not enabled/disabled individually but through the setting. See #39924 (comment))

Note that k8s.node.allocatable.cpu and others defined in SemConv are not yet ported back to the receiver from SemConv: https://opentelemetry.io/docs/specs/semconv/non-normative/k8s-migration/#k8s-node-allocatable-metrics

Tip

_{React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it. Learn more here.}

[github-actions]

Pinging code owners:

• receiver/k8scluster: @dmitryax @TylerHelmuth @povilasv @ChrsMark

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

Pinging code owners for receiver/k8scluster: @dmitryax @TylerHelmuth @povilasv @ChrsMark. See Adding Labels via Comments if you do not have permissions to add labels yourself. For example, comment '/label priority:p2 -needs-triaged' to set the priority and remove the needs-triaged label.

[jaehanbyun]

I wanna work on this issue !

[dmitryax]

@jaehanbyun thank you. it's yours