Allow passing of cluster subnets independently from node subnets

[tabern]

Hello!

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Issue details

Amazon EKS cannot use certain AWS Availability Zones for the cluster control plane. This is true, even when the customer is able to use those zones for nodes.

This should not block customers from using these zones for nodes because it is not required that the subnets given to the cluster are the same subnets used for nodes (see https://docs.aws.amazon.com/eks/latest/userguide/network_reqs.html#network-requirements-subnets and https://aws.github.io/aws-eks-best-practices/networking/subnets/#eks-cluster-architecture).

The current eks.Cluster API specification does not differentiate between subnets passed to the control plane and those used for nodes. This differentiation is allowed in the aws.eks.Cluster provider which is a pass through from the AWS Terraform provider.

Customers need a way in the eks.Cluster provider to specify if a subnet should be used only for the control plane, or alternatively, only for nodes.

Affected area/feature

https://www.pulumi.com/registry/packages/eks/api-docs/cluster/#inputs

[mjeffryes]

Thanks for the suggestion @tabern; getting the right trade off of simplicity and control in the higher-level components is always a challenge. I agree that the availability zones restriction for the control plane, does suggest we should expose this configuration.

If you'd like to propose a change in a PR we will give it a review, otherwise I will put this in the backlog for our team.