Update k8s autodiscover metadata in nodes earlier

[ChrsMark]

What does this PR do?

Node metadata is used by autodiscover to include it in events or
to generate autodiscover hints for the pods in the node.

This change watches explicitly for changes in nodes to update these
metadata immediately instead of waiting for full resyncs.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Closes #23139

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[mergify]

This pull request does not have a backport label. Could you fix it @ChrsMark? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[ChrsMark]

/package

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b pod-node-watcher upstream/pod-node-watcher
git merge upstream/master
git push upstream pod-node-watcher

[elasticmachine]

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Build stats

• Start Time: 2021-12-09T12:02:25.477+0000

• Duration: 158 min 34 sec

• Commit: 20ef0f0

Test stats 🧪

Test	Results
Failed	0
Passed	48593
Skipped	4276
Total	52869

💚 Flaky test report

Tests succeeded.

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[ChrsMark]

/package

[ChrsMark]

/package

[tetianakravchenko]

LGTM!

[ChrsMark]

/package

[jsoriano]

👍

[ChrsMark]

/package