Cluster Duplication for Identical backendRef across Multiple Rules in a Single HTTPRoute

*Description*:
Currently, Envoy Gateway generates a separate cluster per rule in an HTTPRoute, even when all the rules reference the same backendRef. This results in redundant cluster configurations, and lead to:

- Increased memory usage in the Envoy proxy.
- Larger and more complex xDS configurations.
- Longer configuration propagation and reload times.
- Additional overhead when debugging or monitoring Envoy behavior.

Example HTTPRoute snippet
```
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
name: sample-route
spec:
rules:
- matches:
- path:
type: PathPrefix
value: /v1
backendRefs:
- name: my-backend
port: 8080
- matches:
- path:
type: PathPrefix
value: /v2
backendRefs:
- name: my-backend
port: 8080
filters:
- type: URLRewrite
urlRewrite:
path:
replacePrefixMatch: /
type: ReplacePrefixMatch
```
In this example, even though both rules reference the same backend (my-backend:8080), two separate clusters are created in the Envoy config.

Is there a specific reason this behaviour considered? Are there any existing proposals to deduplicate clusters and reuse the single cluster across multiple rules with the same backendRef?