✨ Add MachineHealthCheck node-deleting timeout

[miltalex]

What this PR does / why we need it:

This adds an optional checks.nodeDeleting.timeoutSeconds check to MachineHealthCheck. When configured, MHC treats a Machine as unhealthy if its associated Node has had a deletionTimestamp for longer than the configured timeout. Setting timeoutSeconds: 0 triggers remediation as soon as the Node starts deleting; leaving checks.nodeDeleting unset preserves the existing behavior.
This enables workload-cluster operators to trigger normal Cluster API remediation by deleting a Node, while still respecting the regular remediation flow, drain settings, and Machine deletion behavior.

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 #13591

[kubernetes-prow]

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[kubernetes-prow]

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[kubernetes-prow]

Hi @miltalex. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

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[miltalex]

/ok-to-test

[fabriziopandini]

/hold before review, or possibly close because we have yet an agreed path forward for the problem that this PR is trying to solve (and PR review is not the best way to have those kind of discussions)

see #13591 (comment) (let's discuss first in this issue how the MHC should looks like) and also #13591 (comment) (it would be nice to hear also a few other opinions on this topic)

[kubernetes-prow]

PR needs rebase.

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