[EKS] [request]: Move VPC CNI configuration settings to ConfigMap

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**Tell us about your request**
Add an option for the VPC CNI to pull configuration settings from a Kubernetes ConfigMap

**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?**
Today, all VPC CNI configuration settings must be specified as environment variables on the aws-node daemonset. This can make upgrading difficult, as a new version of the VPC CNI may have a different manifest, but has all default settings. We should be able to follow upgrade instructions without worrying about configuration settings.

**Are you currently working around this issue?**
Download new manifest file, manually edit environment variables, then apply to cluster.

Begin with the EKS aws-node DaemonSet manifest and its current environment-variable configuration. Review how the VPC CNI settings are represented there and determine the ConfigMap integration scope. Done means configuration can be supplied through a Kubernetes ConfigMap while following new manifest upgrade instructions without manually restoring settings.

Written by the indexing model from the issue text.