documentation enhacement

[oliviassss]

Description

Improve the documentations to call out the best practice for setting up the controller deployment.

• Recommend the user to block the instance metadata service for process that do not require access
• For IAM policy configuration, recommend using IRSA over attaching IAM policy to the worker node, and call out the potential risk of attaching the policy directly
• Add a section for node isolation in helm chart

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

Hi @oliviassss. Thanks for your PR.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: oliviassss
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