[EKS] [Fargate]: Ability to modify Default EKS Cluster Security Group for Fargate via Cloudformation

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Tell us about your request
What do you want us to build?
It would be nice if I were able to modify Default EKS Cluster Security Group for Fargate via Cloudformation. if i do not want to use Security group policy https://docs.aws.amazon.com/eks/latest/userguide/security-groups-for-pods.html
https://aws.amazon.com/about-aws/whats-new/2021/06/amazon-eks-pods-running-aws-fargate-support-custom-security-groups/

The only way to edit security group of Fargate pods was to use the way demonstrated in [this document](https://docs.aws.amazon.com/eks/latest/userguide/security-groups-for-pods.html#sg-pods-example-deployment).

Which service(s) is this request for?
Fargate, EKS

Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?
As mentioned above, [this documentation](https://docs.aws.amazon.com/eks/latest/userguide/security-groups-for-pods.html#sg-pods-example-deployment)

Are you currently working around this issue?
Following [https://docs.aws.amazon.com/eks/latest/userguide/security-groups-for-pods.html]
[https://aws.amazon.com/about-aws/whats-new/2021/06/amazon-eks-pods-running-aws-fargate-support-custom-security-groups/]

Begin with the linked EKS security-groups-for-pods documentation and AWS announcement, then verify the current Fargate and CloudFormation behavior for the default cluster security group. Done means the requested security-group modification is supported for Fargate through CloudFormation and the relevant usage is documented.

Written by the indexing model from the issue text.