fix: Correct remote access variable for security groups and add example for additional IAM policies

[bryantbiggs]

Description

• fix vpc remote access variable for security groups to allow for list of security groups; closes fix: Use split function to allow setting multiple source security group ids for remote_access #1762
• update eks-managed-node-group to demonstrate shortcomings of additional IAM policies and security groups, providing an explanation and example for how best to utilize these due to Partial/Progressive Configuration Changes hashicorp/terraform#4149
  • note added to main README to alert and educate users on this issue

Motivation and Context

• Ref Data source for current AWS partition breaks modules #1753 (comment)
• Closes fix: Use split function to allow setting multiple source security group ids for remote_access #1762
• documentation for users on how to use additional resources within the module

Breaking Changes

• No

How Has This Been Tested?

• I have tested and validated these changes using one or more of the provided examples/* projects
  • Validate with eks-managed-node-group example

[bryantbiggs]

I was thinking for a second of adding this policy attachment to the root of the module and handling this for users but that only handles one scenario - where users want to attach a policy to ALL roles created. It would get out of hand rather quickly if we take into consideration where users want a policy attached to specific roles or specific node groups, etc. and decided against it. for now, I think the note added is the best course of action for users at this time

[antonbabenko]

This PR is included in version 18.0.6 🎉

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues. If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.