Migrate ingress to networking.k8s.io/v1beta1

Migrate the ingress template from extensions/v1beta1 to networking.k8s.io/v1beta1.

• What's the migration impact ?

Migrating to the new Ingress API will only require changing the API path - the API fields remain the same

NB: this will be removed in v1.20 - https://kubernetes.io/blog/2019/07/18/api-deprecations-in-1-16/. The networking.k8s.io/v1beta1 has been available since 1.14