admission: use counter type for admission.elastic_cpu.nanos_exhausted…

[sumeerbhola]

…_duration

The metric was already semantically a counter.

Informs #159384

Epic: none

Release note: None

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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[cockroach-teamcity]

This change is 

[blathers-crl]

Metrics change detected

This PR adds or updates one or more CRDB metrics. If you want these metrics to be exported by CRDB Cloud clusters to Internal CRL Datadog and/or included in the customer metric export integration (Essential metrics for standard deployment, and Essential metrics for advanced deployment), refer to this Installation and Usage guide of a CLI tool that syncs the metric mappings in managed-service. Run this CLI tool after your CRDB PR is merged.

• The CLI opens a PR in managed-service with the required config changes.
• Please track that PR and ensure it merges so your metrics become available to CRDB Cloud clusters.

Note: Your metric will appear in Internal CRL Datadog only after the managed-service PR merges and the new OTel configuration rolls out to at least one cluster running a CRDB build that includes this metric.

Docs: cockroach-metric-sync

Questions: reach out to @obs-india-prs