Need to update the multitenancy network-policies section with Amazon VPC CNI latest feature to implement network policies

[praseedasathaye]

Describe the problem
We will need to include the support of the native support for enforcing Kubernetes network policies with Amazon VPC Container Networking Interface (CNI) Plugin. https://aws.amazon.com/blogs/containers/amazon-vpc-cni-now-supports-kubernetes-network-policies/

References
https://aws.github.io/aws-eks-best-practices/security/docs/multitenancy/#network-policies

[jicowan]

Can you submit a PR for this @praseedasathaye?