🚚 moving EKS subnets out of VPC module

[kyphutruong]

This PR moves the EKS-Private subnets out of the VPC module. Reasons explained in this issue

The subnets resources have already been manually moved using the following commands prior to this PR:

terraform state mv 'module.vpc.aws_subnet.private[3]' 'aws_subnet.eks_private[0]'
terraform state mv 'module.vpc.aws_subnet.private[4]' 'aws_subnet.eks_private[1]'
terraform state mv 'module.vpc.aws_subnet.private[5]' 'aws_subnet.eks_private[2]'
terraform state mv 'module.vpc.aws_route_table_association.private[3]' 'aws_route_table_association.eks_private[0]'
terraform state mv 'module.vpc.aws_route_table_association.private[4]' 'aws_route_table_association.eks_private[1]'
terraform state mv 'module.vpc.aws_route_table_association.private[5]' 'aws_route_table_association.eks_private[2]'

Tf plans should output No changes. Your infrastructure matches the configuration.