Add k8s.{pod,node}.cpu.{time,usage} metrics

[ChrsMark]

Changes

This PR adds the k8s.pod.cpu.time, k8s.pod.cpu.usage, k8s.node.cpu.time, k8s.node.cpu.usage metrics.
The respective Collector's implementation can be found at https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/kubeletstatsreceiver/metadata.yaml#L84

Part of #1032.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.

[TylerHelmuth]

These metrics have been in place for 4+ years (except usage, whose rename from utilization is in progress).

[ChrsMark]

@open-telemetry/specs-semconv-approvers could you also take a look?

[lmolkova]

We probably discussed it somewhere, but could you remind me if we have cpu count available for pods/nods and if there are any plans to report it?

[ChrsMark]

We probably discussed it somewhere, but could you remind me if we have cpu count available for pods/nods and if there are any plans to report it?

The k8sclusterreceiver can report the k8s.node.allocatable_cpu so at some point this would be declared in SemConv as well.

The containers define the cpu_limits/cpu_requests, so the the limits/requests of a Pod can be calculated by summarizing its containers' limits/requests.

[TylerHelmuth]

@lmolkova does this repo have merge queue enabled?

[lmolkova]

@lmolkova does this repo have merge queue enabled?

nope, it's all manual. I enabled auto-merge for this one, but all open discussions need to be resolved to allow it to happen.