[Feature] [Application Gateway for Containers] WebApplicationFirewallPolicy should be able to reference Ingress

**Is your feature request related to a problem? Please describe.**
Currently, `WebApplicationFirewallPolicy` can only reference `Gateway` / `HTTPRoute` resources.

**Describe the solution you'd like**
Since ALB Controller implements the Ingress API, `WebApplicationFirewallPolicy` should be able to reference `Ingress` resources.

**Additional context**
Gateway API has an architectural problem with regards to TLS certificate references as highlighted in https://github.com/Azure/AKS/issues/5333. That will be solved with `ListenerSet` ([GEP-1713: ListenerSets - Standard Mechanism to Merge Multiple Gateways](https://gateway-api.sigs.k8s.io/geps/gep-1713/)) but that's still in experimental channel. Until that's implemented, the only realistic option I've come up with to use namespaced TLS certificates, is to use the Ingress API to configure AGC.