Merge Gateway Prometheus Virtual Host metrics random assigned wrong with multiple listeners

Description: Prometheus Virtual Host metrics are being assigned wrongly having cases where the wrong host is being attached to the wrong vhost.

I am not sure what the correct behaviour is in some cases we just get metrics like envoy_vhost_vcluster_upstream_rq_retry and in the current case we get vhost.<virtual host name>.vcluster.<virtual cluster name> which is what the envoy docs say but with the wrong virtual host name attached to the wrong virtual host cluster.

A. The envoy_vhost_vcluster_upstream_rq_retry metrics that get emitted do have labels for envoy_virtual_cluster and envoy_virtual_host

B. vhost.<virtual host name>.vcluster.<virtual cluster name> only have the envoy_virtual_host label attached and no cluster label.

I hope A is the correct way as its easier to build dashboards from.

Repro steps:

Take a example :

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: foo
spec:
  gatewayClassName: merge-gateway
  listeners:
  - name: foo.com
    protocol: HTTP
    hostname: foo.com
    port: 80
    allowedRoutes:
      namespaces:
        from: Same
  - name: bar.com
    protocol: HTTP
    hostname: bar.com
    port: 80
    allowedRoutes:
      namespaces:
        from: Same
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: foobar-combined
spec:
  parentRefs:
    - name: foo
      group: gateway.networking.k8s.io
      kind: Gateway 
  hostnames:
  - foo.com
  - foobar.com
  rules:
  - backendRefs:
    - kind: Service
      group: ''
      name:  my-svc
      port: 80
      weight: 1
    matches:  
    - path:
        type: PathPrefix
        value: /
---
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: a
spec:
  gatewayClassName: merge-gateway
  listeners:
  - name: a.foo.com
    protocol: HTTP
    hostname: foo.com
    port: 80
    allowedRoutes:
      namespaces:
        from: Same
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: a
spec:
  parentRefs:
    - name: foo
      group: gateway.networking.k8s.io
      kind: Gateway 
  hostnames:
  - a.foo.com
  rules:
  - backendRefs:
    - kind: Service
      group: ''
      name:  my-svc
      port: 80
      weight: 1
    matches:  
    - path:
        type: PathPrefix
        value: /
---
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: ab
spec:
  gatewayClassName: merge-gateway
  listeners:
  - name: ab.foo.com
    protocol: HTTP
    hostname: ab.foo.com
    port: 80
    allowedRoutes:
      namespaces:
        from: Same
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: foobar-combined
spec:
  parentRefs:
    - name: ab
      group: gateway.networking.k8s.io
      kind: Gateway 
  hostnames:
  - ab.foo.com
  rules:
  - backendRefs:
    - kind: Service
      group: ''
      name:  my-svc
      port: 80
      weight: 1
    matches:  
    - path:
        type: PathPrefix
        value: /

Its hard to pinpoint what's going on and seems to be random in how it picks for example I got envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry{envoy_virtual_host="api-gateway/ab/ab"} 0 for the metric name.

Metrics dump

# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry counter
envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry_limit_exceeded counter
envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry_limit_exceeded{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry_overflow counter
envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry_overflow{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry_success counter
envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_retry_success{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_timeout counter
envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_timeout{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_total counter
envoy_vhost_foo_com_ab_foo_com_vcluster_ab_foo_com_upstream_rq_total{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry counter
envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry_limit_exceeded counter
envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry_limit_exceeded{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry_overflow counter
envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry_overflow{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry_success counter
envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_retry_success{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_timeout counter
envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_timeout{envoy_virtual_host="api-gateway/ab/ab"} 0
# TYPE envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_total counter
envoy_vhost_foo_com_ab_foo_com_vcluster_other_upstream_rq_total{envoy_virtual_host="api-gateway/ab/ab"} 0

it looks like its merging the virtual clusters.

Environment: k8s 1.29.0 envoy gateway 1.0.1 Merge gateways