[EKS] [request]: MapGroups in ConfigMap

**Tell us about your request**
In order to grant access to a group of users to an EKS cluster, I'd like to map a whole IAM group in the ConfigMap. Similar to "mapRoles" and "mapUsers", I'd like to use something like "mapGroups" and inform a group arn.

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
In order to map a group of users to grant access to the EKS cluster, with current configMap specifications, the way to do it is to map each individual user by editing the configMap with "mapUsers".

**Are you currently working around this issue?**
The current workaround for this is to create a IAM policy that allows the group to assume a role that has access to the cluster and is mapped in the configMap. Then, assume the role before accessing the cluster with a command like: aws sts assume-role --role-arn arn:aws:iam::123456789:role/EKS-test-role --role-session-name

**Additional context**
Please let me know if this is a valid feature request. Maybe there's something here I'm missing, but I think it should be ok to map a IAM group arn to grant access to the EKS cluster.

Start by reviewing the EKS ConfigMap specifications and the existing mapRoles and mapUsers entries mentioned in the request. Compare the proposed mapGroups IAM group ARN with the documented assume-role workaround; done would mean a confirmed EKS feature design or implementation that grants group access directly through the ConfigMap.

Written by the indexing model from the issue text.