[bug fix] handle ram shared VPCs for cross account tgb

[zac-nixon]

Issue

#4089

Description

The initial implementation didn't account for RAM shared VPCs, targets in target groups that use RAM shared VPCs can't set the AZ = 'all' as the VPC exists in the account that owns the target group.

This CR adds support to handle either peered VPCs (which will return not found when we resolve the VPC as we use the cluster accounts' credentials to resolve the VPC) and RAM shared VPCs (which will get resolved from the resolve VPC call).

I wsa able to test this out in my own cluster using a peered VPC and RAM shared VPC. Furthermore, I backfilled some missing tests and reiterated the fix details in the code.

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 🌟

[shraddhabang]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shraddhabang, zac-nixon

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