Identify VPC by resource tags

[cathal-c]

Issue

Addresses #3644.

Description

This PR introduces a new runtime argument, aws-vpc-tag-key which is used to identify VPCs, from which we can infer the VPC ID.

This is useful for cases where access to AWS metadata is blocked and the VPC ID is not known at deploy time, options to infer the VPC ID are limited.

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]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: CathalC2011
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[M00nF1sh]

shall we consider to have aws-vpc-tags= and make it a string map?
seems that's would be more general as in my sample vpcs, i only have a name: vpc-name tag.

for your use case, it can expressed as aws-vpc-tags=<yourTagKey>:owned.

[jeswinkoshyninan]

@M00nF1sh thank you for your comments, it looks good to me. Please note that I am from Cathal's team and since he is away, I am taking over this request and changes based on your comments are now added into a new PR: https://github.com/kubernetes-sigs/aws-load-balancer-controller/pull/3656/files. please take a look into the same.

[k8s-ci-robot]

PR needs rebase.

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