Migrate usage of IAM to aws-sdk-go-v2

[cPu1]

Description

Migrates usage of IAM to aws-sdk-go-v2. One notable change is that a new interface ResourceSetReader, containing a subset of the ResourceSet methods, has been added.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes
• (Core team) Added labels for change area (e.g. area/nodegroup) and kind (e.g. kind/improvement)

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 🌟

[Skarlso]

A single comment and one question... You mix Background and TODO for context here and there. What makes you choose one over the other? :)

[cPu1]

A single comment and one question... You mix Background and TODO for context here and there. What makes you choose one over the other? :)

I have used context.Background() in tests where we don't need to worry about supplying an appropriate Context. context.TODO() is used in the main code to ensure we revisit this later and determine if a deadline-based or cancellable Context can be used.

[nikimanoledaki]

context.TODO() is used in the main code to ensure we revisit this later and determine if a deadline-based or cancellable Context can be used.

Is there a new issue to track this?

[cPu1]

context.TODO() is used in the main code to ensure we revisit this later and determine if a deadline-based or cancellable Context can be used.

Is there a new issue to track this?

I have created one: #5093.

[Himangini]

LGTM