[Feature] Remove client-side validation of cluster Kubernetes version

[cartermckinnon]

What feature/behavior/change do you want?

I want the client-side validation of cluster Kubernetes versions to be removed. The EKS API(s) will return an error if a requested version is invalid. At a minimum, this validation should be controlled with a config option, environment variable, etc.

Why do you want this feature?

Different users (and developers 😄) have access to different Kubernetes versions. It's annoying that I can't use eksctl to create a cluster on an upcoming (or deprecated) Kubernetes version, for example. Of course there are apiVersion-s to consider, but in most cases things will just work -- I just want the ability to try the request regardless.