Attempt to get genegraph UI and genegraph on the same hostname for CORS purposes

[sjahl]

See: https://clingen.slack.com/archives/C01S7GH0GJF/p1644346884505619

In environments that MITM you and inject CORS headers on http responses, it's problematic to have genegraph-ui being served from a different hostname than genegraph.

I'm not 100% on this yet, but GKE Ingress supports the use of cloud CDN, so we may be able to achieve this by using that.

https://cloud.google.com/kubernetes-engine/docs/how-to/ingress-features

Some quick searches indicate that there's some performance considerations: https://blog.yongweilun.me/gke-ingress-is-slower-than-you-think