What would you like to be added:
I would like a feature like istio Gateway. The use-case is the same:

1. We have GlooEdge Proxy + ClusterIP service
2. We have an Ingress which provide external access to above Proxy

So the idea is having a way to specify ingress which is backing a specific Gateway/Proxy

Why is this needed:

This is our use-case. The reason behind is that using ALB, we can put an AWS WAF in front of Gloo Proxy

I'm happy to work on this and will come with a PR later