Revert "Merge branch 'gy-aws-rails-additional-sg-ids' into 'main'"

What does this MR do?

MR reverts !873 (merged) as it was dependent on !871 (merged), which itself had to be reverted due to it having the unintended consequence of breaking cloud native hybrids as security group membership of an EKS cluster doesn't apply to the Node Groups surprisingly (and therefore doesn't filter through).

As a result we need to switch back to a CIDR based approach for now as we explore other options (such as possibly switching to launch templates). The option given in this MR is useless here as the default CIDR is wider.

Related issues

Relates #569 (closed)

Author's checklist

When ready for review, the Author applies the workflowready for review label and mention @gl-quality/get-maintainers:

• Merge request:
  • Corresponding Issue raised and reviewed by the GET maintainers team.
  • Merge Request Title and Description are up-to-date, accurate, and descriptive
  • MR targeting the appropriate branch
  • MR has a green pipeline
  • MR has no new security alerts in the widget from the Secret Detection and IaC Scan (SAST) jobs.
• Code:
  • Check the area changed works as expected. Consider testing it in different environment sizes (1k,3k,10k,etc.).
  • Documentation created/updated in the same MR.
  • If this MR adds an optional configuration - check that all permutations continue to work.
  • For Terraform changes: set up a previous version environment, then run a terraform plan with your new changes and ensure nothing will be destroyed. If anything will be destroyed and this can't be avoided please add a comment to the current MR.
• Create any follow-up issue(s) to support the new feature across other supported cloud providers or advanced configurations. Create 1 issue for each provider/configuration. Contact the Quality Enablement team if unsure.