feat: tag subnets manually if not creating vpc

[dali546]

Description

a cluster with version 1.19+ no longer creates subnet tags automatically.

And also when not creating a VPC, we still need to tag the subnets as public or private

This commit adds the relavant tags.

Source: https://docs.aws.amazon.com/eks/latest/userguide/network_reqs.html#vpc-subnet-tagging and also https://docs.aws.amazon.com/eks/latest/userguide/alb-ingress.html