fix: use upstream id instead of inline upstream in traffic-split plugin

[ronething]

Type of change:

• Bugfix
• New feature provided
• Improve performance
• Backport patches
• Documentation
• Refactor
• Chore
• CI/CD or Tests

What this PR does / why we need it:

ref: #2540 (comment)

In the traffic-split plugin, use upstream_id to replace inline upstream.

• dataplane config example:

{
  "upstreams_conf_version": 1757381144237,
  "services": [
    {
      "modifiedIndex": 1757381144237,
      "labels": {
        "k8s/kind": "HTTPRoute",
        "k8s/name": "httpbin",
        "k8s/namespace": "ingress-apisix-e2e-tests-default-382127000",
        "k8s/controller-name": "apisix.apache.org/apisix-ingress-controller/ingress-apisix-e2e-tests-default-382127000",
        "manager-by": "apisix-ingress-controller"
      },
      "hosts": [
        "httpbin.example"
      ],
      "plugins": {
        "traffic-split": {
          "rules": [
            {
              "weighted_upstreams": [
                {
                  "weight": 100
                },
                {
                  "weight": 0,
                  "upstream_id": "132f5f83"
                }
              ]
            }
          ]
        }
      },
      "upstream_id": "25898fae",
      "name": "ingress-apisix-e2e-tests-default-382127000_httpbin_0",
      "id": "25898fae"
    }
  ],
  "X-Digest": "4e8c5200539290ec21f0bbdd1b9ea0df99d8241b",
  "upstreams": [
    {
      "modifiedIndex": 1757381144237,
      "labels": {
        "managed-by": "apisix-ingress-controller"
      },
      "nodes": [
        {
          "weight": 100,
          "port": 80,
          "host": "10.244.0.53"
        }
      ],
      "scheme": "http",
      "type": "roundrobin",
      "name": "ingress-apisix-e2e-tests-default-382127000_httpbin_0",
      "id": "25898fae"
    },
    {
      "modifiedIndex": 1757381144237,
      "labels": {
        "managed-by": "apisix-ingress-controller",
        "__ADC_UPSTREAM_SERVICE_ID": "25898fae"
      },
      "nodes": [
        {
          "weight": 0,
          "port": 80,
          "host": "10.244.0.56"
        },
        {
          "weight": 0,
          "port": 80,
          "host": "10.244.0.57"
        }
      ],
      "scheme": "http",
      "type": "roundrobin",
      "name": "Service_ingress-apisix-e2e-tests-default-382127000_nginx_80",
      "id": "132f5f83"
    }
  ],
  "X-Last-Modified": 1757381144,
  "services_conf_version": 1757381144237
}

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[Copilot]

Pull Request Overview

This PR refactors the traffic-split plugin implementation to use upstream IDs instead of inline upstream objects, improving the dataplane configuration structure. The change ensures that upstreams are properly referenced by ID in traffic-split configurations while maintaining separate upstream definitions.

• Replace inline upstream objects with upstream_id references in traffic-split plugin
• Add proper upstream naming and ID generation for backend references
• Update Service struct to include an Upstreams field for managing multiple upstream definitions

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/adc/translator/httproute.go	Adds upstream naming/ID generation and uses upstream_id in traffic-split configurations
internal/adc/translator/apisixroute.go	Updates ApisixRoute translator to use upstream_id references and proper naming
api/v2/shared_types.go	Adds utility functions for composing upstream names
api/adc/types.go	Adds Upstreams field to Service struct
api/adc/zz_generated.deepcopy.go	Generated deep copy methods for new Upstreams field
.github/workflows/apisix-e2e-test.yml	Sets ADC_VERSION environment variable

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[bzp2010]

Are our tests based on the final results? Do they not need to be modified to verify the changes in the pull request?

[ronething]

Are our tests based on the final results? Do they not need to be modified to verify the changes in the pull request?

The current test should be sufficient. If necessary, we can consider creating a new issue to track some more detailed assertions in the test.

• apisixroute:

  apisix-ingress-controller/test/e2e/crds/v2/route.go

  Lines 810 to 811 in 0a7b040

  	Context("Test ApisixRoute Traffic Split", func() {
  	It("2:1 traffic split test", func() {

• httproute:

  apisix-ingress-controller/test/e2e/gatewayapi/httproute.go

  Lines 2030 to 2031 in f172410

  	It("HTTPRoute Canary", func() {
  	s.ResourceApplied("HTTPRoute", "httpbin", fmt.Sprintf(sameWeiht, s.Namespace()), 1)