Rename Windows warm/minimum IP targets

[jdn5126]

What would you like to be enhanced:
I would like to rename the Windows warm/minimum IP target variables that are read from the amazon-vpc-cni ConfigMap: https://github.com/aws/amazon-vpc-resource-controller-k8s/blob/master/pkg/config/type.go#L76

The current names cause confusion with the environment variables in the aws-node Daemonset that are used for warm/minimum targets on Linux nodes. I propose that we rename these to windows-*.

Since we cannot do the switchover all at once, I propose the VPC Resource Controller starts accepting both names, which will allow the AWS VPC CNI chart to change its names to the windows-* values.

Why is the change needed and what use case will it solve:
This change would help avoid customer confusion when it comes to deploying the AWS VPC CNI chart.

[haouc]

Thanks @jdn5126 , it makes sense to rename them to be aligned with Windows use case and avoid confusion with Linux use cases.