[EKS] [feature-request]: Support Vanity URLs for API Server Endpoint

**Tell us about your request**
Right now, the API server endpoint is generated when the cluster is created. Ideally, I would like to be able to specify a vanity URL(s) when creating the cluster which would resolve to the API server endpoint of the cluster.

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
When I want to try out new, cluster-wide changes, I typically bring up an entirely new cluster with the new configuration, migrate workloads from the existing cluster to it, and redirect traffic over. All of the tooling that needs to access the cluster needs to be updated to have the new cluster endpoint when this happens. For example, developers have a kubeconfig on their laptops in order to access the Kubernetes API. When I cutover to a new cluster, all developers need to update their kubeconfig. Ideally, I could set everyone up with a kubeconfig with cluster1.example.com and cluster2.example.com. cluster1.example.com and cluster2.example.com would resolve to API server endpoints in EKS. If I decide to cutover to cluster1.example.com in EKS and bring up a new cluster, I should be able to configure the new cluster such that cluster1.example.com resolves to it. This would be a transparent change from the perspective of tooling - no changes would be required.

**Are you currently working around this issue?**
All tooling that requires access to the Kubernetes API needs to be updated every time I swap clusters.