feat(pvc): support kube_persistentvolumeclaim_deletion_timestamp

[maxime1907]

What this PR does / why we need it:
Adds a simple metric kube_persistentvolumeclaim_deletion_timestamp so that we can detect PVCs in "Terminating" state

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

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 #1437

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[dgrisonnet]

/triage accepted

[maxime1907]

any update on this ? @mrueg @dgrisonnet

[mrueg]

/lgtm

Thanks a lot for your contribution!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: maxime1907, mrueg

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