Improve RBAC management for aws-auth

[jpolchlo]

The EKS module gives the ability to configure the aws-auth ConfigMap to give users and roles access to the cluster. That can be for administration or monitoring purposes using local tools like kubectl or Lens. The problem is that the EKS module appears to have a dependency problem where it attempts to apply configurations to aws-auth before the ConfigMap is set up. I'm not overly thrilled with the solution being to create the cluster with the [manage_aws_auth_configmap](https://registry.terraform.io/modules/terraform-aws-modules/eks/aws/latest#input_manage_aws_auth_configmap) option set to false, and then update the configuration with this setting enabled, which is an obvious hack.

This issue is to resolve this problem definitively. A solution might be to file an issue to the module github, or to develop a more complex solution in-house, or to just implement the hack described above as a stop-gap.