OCPBUGS-42805: Add node caching with Kubernetes watch API to reduce API load

[mkowalski]

Replace frequent node LIST calls with a watch-based cache in monitor loops. Implements NodeWatcher similar to existing loggingconfig watcher pattern.

• Add pkg/nodeconfig with NodeWatcher and NodeCacheGetter interface
• Refactor node retrieval functions to use cache when available
• Update monitors (dynkeepalived, coredns) to use NodeWatcher
• Reduce API calls from hundreds/min to single watch connection
• Maintain backward compatibility with nil cache fallback

Fixes: OCPBUGS-42805

[openshift-ci-robot]

@mkowalski: This pull request references Jira Issue OCPBUGS-42805, which is invalid:

• expected the bug to target the "4.21.0" version, but no target version was set

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

The bug has been updated to refer to the pull request using the external bug tracker.

In response to this:

Replace frequent node LIST calls with a watch-based cache in monitor loops. Implements NodeWatcher similar to existing loggingconfig watcher pattern.

• Add pkg/nodeconfig with NodeWatcher and NodeCacheGetter interface
• Refactor node retrieval functions to use cache when available
• Update monitors (dynkeepalived, coredns) to use NodeWatcher
• Reduce API calls from hundreds/min to single watch connection
• Maintain backward compatibility with nil cache fallback

Fixes: OCPBUGS-42805

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[mkowalski]

/test e2e-metal-ipi-ovn-dualstack /test e2e-metal-ipi-ovn-ipv4

[mkowalski]

/hold

I don't want it for 4.21; will be on hold till branch cut and should land only in 4.22

[mkowalski]

/test e2e-metal-ipi-ovn-dualstack /test e2e-metal-ipi-ovn-ipv4

Conformance failures

{  fail [github.com/openshift/origin/test/extended/apiserver/tls.go:151]: Expected success true, got false with TLS version VersionTLS12 dialing master}

[openshift-ci[bot]]

@mkowalski: all tests passed!

Full PR test history. Your PR dashboard.

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[cybertron]

/lgtm

Looks like a good way to address a longstanding issue!

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cybertron, mkowalski

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