* aws_eks_cluster: Improve output documentation
This data is already returned by the module, it just wasn't documented. These
fields are required for accessing the created Kubernetes API with e.g. the
k8s_raw module.
* aws_eks_cluster: Add wait functionality
This enables further cluster configuration once it's created and active.
20 minutes was chosen as an arbitrary default, so that if it takes longer than
the documented "usually less than 10 minutes" it's still likely to succeed.
* Correct security group name in aws_eks tests
* Improve teardown of aws_eks tests
Fix minor teardown issues. The `pause` step is a placeholder until
a waiter for `state: absent`