feat: introduce deletion timestamp metric for multiple resources

[IgorIgnatevBolt]

What this PR does / why we need it:

Some resources can be blocked by deletion from finalizers. To catch this and expose it to metrics, we can use the deletion timestamp metadata field. Introduce a deletion_timestamp metric for the next resources:

• deployment kube_deployment_deletion_timestamp
• statefulset kube_statefulset_deletion_timestamp
• daemonset kube_daemonset_deletion_timestamp
• service kube_service_deletion_timestamp
• poddisruptionbudget kube_poddisruptionbudget_deletion_timestamp

Also formatting tables in docs

How does this change affect the cardinality of KSM: (increases, decreases or does not change cardinality)

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #

[IgorIgnatevBolt]

All commits were squashed into one.

[CatherineF-dev]

Hi, could you share more insights on use cases after these metrics are added?

Is it used for monitoring Kubernetes resources that are stuck in a terminating state?

[IgorIgnatevBolt]

@CatherineF-dev Hi, yes, if the resource deletion process is stuck for some reason or blocked by the finalizer, deletiontimestamp metric can help to detect such a case and raise an alert for investigation.

[richabanker]

/assign

[CatherineF-dev]

@IgorIgnatevBolt How will we know which resource should be deleted?

[IgorIgnatevBolt]

@IgorIgnatevBolt How will we know which resource should be deleted?

Maybe I misunderstood the question, but this PR is exactly about detection for such resources that were nominated by the controller manager for deletion but not deleted for some reason, eq blocked by finalizers

The controller managing that finalizer notices the update to the object setting the metadata.deletionTimestamp, indicating deletion of the object has been requested.

[IgorIgnatevBolt]

Hi @CatherineF-dev, do you need any more information about PR or anything else that can help you move forward?

[dgrisonnet]

/assign @CatherineF-dev /triage accepted

[IgorIgnatevBolt]

rebased, conflicts solved

[IgorIgnatevBolt]

fixed typo in the depl test

[mrueg]

/hold

for @CatherineF-dev to further comment. Renamed the title to include all additional resources in there.

/lgtm

[k8s-ci-robot]

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[mrueg]

/hold cancel