Fix weighted route

[zhaohuabing]

fix #2170

Envoy requires a distinct region to be set for each LocalityLbEndpoints. If we don't do this, Envoy will merge all LocalityLbEndpoints into one. In this PR, the name of the backendRef is used as a pseudo region name to avoid this issue.

HTTPRoute

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: http-headers
  namespace: default
spec:
  hostnames:
  - backends.example
  parentRefs:
  - group: gateway.networking.k8s.io
    kind: Gateway
    name: eg
  rules:
  - backendRefs:
    - group: ""
      kind: Service
      name: backend
      port: 3000
      weight: 8
    - group: ""
      kind: Service
      name: backend-2
      port: 2000
      weight: 2
    matches:
    - path:
        type: PathPrefix
        value: /

EDS

"dynamicEndpointConfigs": [
        {
          "endpointConfig": {
            "@type": "type.googleapis.com/envoy.config.endpoint.v3.ClusterLoadAssignment",
            "clusterName": "httproute/default/http-headers/rule/0",
            "endpoints": [
              {
                "lbEndpoints": [
                  {
                    "endpoint": {
                      "address": {
                        "socketAddress": {
                          "address": "10.244.0.8",
                          "portValue": 3000
                        }
                      },
                      "healthCheckConfig": {}
                    },
                    "healthStatus": "HEALTHY",
                    "loadBalancingWeight": 1
                  }
                ],
                "loadBalancingWeight": 8,
                "locality": {
                  "region": "httproute/default/http-headers/rule/0/backend/0"
                }
              },
              {
                "lbEndpoints": [
                  {
                    "endpoint": {
                      "address": {
                        "socketAddress": {
                          "address": "10.244.0.10",
                          "portValue": 2000
                        }
                      },
                      "healthCheckConfig": {}
                    },
                    "healthStatus": "HEALTHY",
                    "loadBalancingWeight": 1
                  }
                ],
                "loadBalancingWeight": 2,
                "locality": {
                  "region": "httproute/default/http-headers/rule/0/backend/1"
                }
              }
            ],
            "policy": {
              "overprovisioningFactor": 140
            }
          }
        }
      ],

[arkodg]

LGTM thanks for solving this one !

[arkodg]

gen-check is failing , can you run make testdata

[zhaohuabing]

@arkodg how about changing the locality name to "httproute/default/http-headers/rule/0/backend/0? backend is clearer than setting.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f92da90) 64.17% compared to head (7fa2aa0) 64.22%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2187      +/-   ##
==========================================
+ Coverage   64.17%   64.22%   +0.05%     
==========================================
  Files         107      107              
  Lines       14922    14924       +2     
==========================================
+ Hits         9576     9585       +9     
+ Misses       4770     4764       -6     
+ Partials      576      575       -1     

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