feat: Enable ai-statistics plugin for AI routes by default

[CH3CHO]

Ⅰ. Describe what this PR did

Enable ai-statistics plugin for AI routes by default.

apiVersion: extensions.higress.io/v1alpha1
kind: WasmPlugin
metadata:
  annotations:
    higress.io/wasm-plugin-description: Provides statistics of token usage, including
      logs, monitoring, and alerts.
    higress.io/wasm-plugin-icon: https://img.alicdn.com/imgextra/i1/O1CN018iKKih1iVx287RltL_!!6000000004419-2-tps-42-42.png
    higress.io/wasm-plugin-title: AI Statistics
  creationTimestamp: "2025-01-14T04:18:57Z"
  generation: 2
  labels:
    higress.io/resource-definer: higress
    higress.io/wasm-plugin-built-in: "true"
    higress.io/wasm-plugin-category: ai
    higress.io/wasm-plugin-name: ai-statistics
    higress.io/wasm-plugin-version: 1.0.0
  name: ai-statistics-1.0.0
  namespace: higress-system
  resourceVersion: "2945137"
  uid: bde30c13-b17d-4611-977a-ad52b0e228bd
spec:
  defaultConfigDisable: true
  failStrategy: FAIL_OPEN
  matchRules:
  - config:
      attributes:
      - apply_to_log: true
        key: question
        value: messages.@reverse.0.content
        value_source: request_body
      - apply_to_log: true
        key: answer
        rule: append
        value: choices.0.delta.content
        value_source: response_streaming_body
      - apply_to_log: true
        key: answer
        value: choices.0.message.content
        value_source: response_body
    configDisable: false
    ingress:
    - ai-route-qwen.internal
  - config:
      attributes:
      - apply_to_log: true
        key: question
        value: messages.@reverse.0.content
        value_source: request_body
      - apply_to_log: true
        key: answer
        rule: append
        value: choices.0.delta.content
        value_source: response_streaming_body
      - apply_to_log: true
        key: answer
        value: choices.0.message.content
        value_source: response_body
    configDisable: false
    ingress:
    - ai-route-qwen.fallback.internal
  phase: UNSPECIFIED_PHASE
  priority: 900
  url: oci://higress-registry.cn-hangzhou.cr.aliyuncs.com/plugins/ai-statistics:1.0.0

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[johnlanni]

LGTM