AWS::EC2::VPCEndpoint return ENI IP address

For interface typed VPC endpoints it would be good to have the private IPs of the ENIs as an attribute accessible via !GetAtt.

For several use cases, DNS names are not enough and you need the IP of the ENI.

Currently, this can only be solved by a custom resource that takes the ENIs (`!GetAtt VPCE.NetworkInterfaceIds`) and resolves them to IPs.

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-vpcendpoint.html

Category: Networking & Content (VPC, Route53, API GW,...)

Start with the AWS::EC2::VPCEndpoint resource documentation linked in the issue and its current attribute list. Confirm how interface endpoint ENI IDs are exposed; done when private ENI IPs are available through !GetAtt without the described custom resource.

Written by the indexing model from the issue text.