Use AWS managed IAM policies instead of custom policies

[pbobov]

The README files of the AWS templates for each workflow should specify AWS managed policies instead of custom IAM policies .

Custom policies can offer more precise access control by minimizing privileges, but they can be challenging to manage and are most effective when tailored to specific resources.

[pbobov]

After some research I've changed my mind on this.

1. There are no suitable AWS managed policies for some services. In particular, there are not AWS managed policies that have eks:CreateCluster (required to create AKS cluster) and eks:DescribeCluster (required by "aws eks update-kubeconfig").
2. Unlike Azure policies, AWS managed policies are either to permissive (*FullAccess) or too restrictive/specialized.