feat: Eliminated the use of temporary keys for tests with kubectl in privatelink-access pattern

[vchintal]

Description

The privatelink-access pattern documentation had steps which involved creating temporary set of AWS credentials for the use of testing PrivateLink connectivity. This approach is manual and copy pasting credentials, however short-lived isn't ideal.

With the new set of changes introduced in this PR:

1. The EKS cluster would initially come up with its API endpoint as public
2. This would ensure that the Client EC2 instance's attached role is added as system:masters in aws-auth configmap
3. Which would allow the Client EC2 to run kubectl commands as an Admin against the EKS cluster in the Client VPC without the need for any credentials
4. The documentation is also corrected to:
   • Include the right steps to deploy the pattern
   • Include steps to take the cluster API endpoint private after Terraform finishes
   • Include cleaner steps to test the pattern
   • Add additional step of take the cluster API endpoint public before tearing down the resources

How was this change tested?

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Yes, I ran pre-commit run -a with this PR