Support dual stack endpoints

[zoellner]

The url schema for the dual stack endpoints is different from the old IPv4 only endpoints
Domain endpoint (IPv4)
https://{{domainId}}.{{region}}.es.amazonaws.com
Domain endpoint v2 (dual stack)
https://{{domainId}}.aos.{{region}}.on.aws

Using the new dual stack endpoint currently does not work:

region cannot be parsed from endpoint address, either the endpoint must end in .<region>.es.amazonaws.com or --region should be provided as an argument
usage: aws-es-kibana [options] <aws-es-cluster-endpoint>