Resolve "Add ability to not configure AWS Object Storage IAM resources"

What does this MR do?

This merge request updates the documentation and code for the object storage feature in GitLab's AWS infrastructure. It introduces new optional settings for object storage, including the ability to control IAM resource creation, specify instance profile names for GitLab Rails and Sidekiq, and configure replication-related settings. Additionally, it updates the Terraform modules to use these new settings and adds a new data source to retrieve the IAM role ARN for object storage replication. These changes provide more flexibility and control over object storage configuration in GitLab's AWS environment.

Related issues

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 Self-Managed Platform team if unsure.

@gl-quality/get-maintainers Closes #970 (closed)