feat: add apiserver_admission_webhook_request_total metric

[jwillker]

What does this PR do?

This PR adds a new kubernetes metric: apiserver_admission_webhook_request_total
More details: https://kubernetes.io/docs/reference/instrumentation/metrics/

This metric was created in the kubernetes 1.23 version: kubernetes/kubernetes#103162

Fix: #17689

Motivation

This metric is missing in the Datadog Kubernetes integration.

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Changelog entries must be created for modifications to shipped code
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.80%. Comparing base (4013d3c) to head (2985228).
Report is 1 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
dotnetclr	?
gitlab	?
hive	?
hivemq	?
hudi	?
ignite	?
jboss_wildfly	?
kafka	?
kube_apiserver_metrics	97.75% <100.00%> (+0.01%)	⬆️
kubeflow	?
kubevirt_api	?
kubevirt_controller	?
marklogic	?
presto	?
snmp	?
solr	?
vertica	?
windows_service	?

Flags with carried forward coverage won't be shown. Click here to find out more.

[jwillker]

@FlorentClarret I don't understand what is wrong with the tests. Can you help me?

[jwillker]

Would anyone be able to help me with this PR?

@Kyle-Neale, @jmeunier28, @dkirov-dd or someone else?

[sblumenthal]

Thank you for the contribution!

I think the metric does in fact make sense and sounds useful, and the PR itself looks good to me. I added one small suggestion, to add the metric stability level and supported k8s version to the documentation, but otherwise I am happy to approve this afterwards