【enhancement】add policy event, report to backend

[robotLJW]

【修复issue】#1176

【修改内容】
Policy事件包含三件：
1.相同标签规则匹配成功: 全部实例最小可用阈值大于全部可用实例数，则同TAG优先
2.相同标签规则匹配成功:
未设置全部实例最小可用阈值，超过(大于等于)同TAG比例阈值，则同TAG优先
设置了全部实例最小可用阈值，但其小于全部TAG可用实例，超过(大于等于)同TAG比例阈值，则同TAG优先
3.相同标签规则匹配失败

【用例描述】无

【自测情况】（feign，rest，dubbo）：只会上报前后两次状态不同的事件
应用：一个带gray:red的parameter且版本为1.0.1的consumer
三个provider分别是：

1. 带group:abcd的parameter
2. 带group:abc的parameter
3. 版本为1.0.0

模拟请求：

curl  ip:port/router/cloud/getMetadata

场景一：policy中仅设置比例阈值为20%，同TAG优先

---
- kind: routematcher.sermant.io/tag
  description: aaa
  rules:
    - precedence: 1
      match:
        tags:
          group:
            exact: abc
        policy:
          triggerThreshold: 20
      route:
        - tags:
            gray: CONSUMER_TAG

验证：同TAG优先，一直访问到带red的下游服务

backend界面：同TAG优先规则匹配生效

---

场景二：policy中仅设置比例阈值为50%，非同TAG优先，随机访问ALL

---
- kind: routematcher.sermant.io/tag
  description: aaa
  rules:
    - precedence: 1
      match:
        tags:
          group:
            exact: abc
        policy:
          triggerThreshold: 50
      route:
        - tags:
            gray: CONSUMER_TAG

验证：非同TAG优先，随机访问

backend界面：同TAG优先规则匹配失效

---

场景三：policy中设置比例阈值为20%和最小可用实例阈值4，同TAG优先

---
- kind: routematcher.sermant.io/tag
  description: aaa
  rules:
    - precedence: 1
      match:
        tags:
          group:
            exact: abc
        policy:
          triggerThreshold: 20
          minAllInstances: 4
      route:
        - tags:
            gray: CONSUMER_TAG

验证：同TAG优先，一直访问到带red的下游服务

backend界面：同TAG优先规则匹配生效

---

场景四：policy中设置比例阈值为20%和最小可用实例阈值1，同TAG优先

---
- kind: routematcher.sermant.io/tag
  description: aaa
  rules:
    - precedence: 1
      match:
        tags:
          group:
            exact: abc
        policy:
          triggerThreshold: 20
          minAllInstances: 1
      route:
        - tags:
            gray: CONSUMER_TAG

验证：同TAG优先，一直访问到带red的下游服务

backend界面：同TAG优先规则匹配生效

---

场景五：policy中设置比例阈值为50%和最小可用实例阈值1，非同TAG优先，随机访问ALL

---
- kind: routematcher.sermant.io/tag
  description: aaa
  rules:
    - precedence: 1
      match:
        tags:
          group:
            exact: abc
        policy:
          triggerThreshold: 50
          minAllInstances: 1
      route:
        - tags:
            gray: CONSUMER_TAG

验证：非同TAG优先，随机访问ALL

backend界面：同TAG优先规则匹配失效

【影响范围】是需要更新一些文档（router手册）

[codecov]

Codecov Report

Patch coverage: 68.96% and project coverage change: +0.58 🎉

Comparison is base (e6167c0) 41.57% compared to head (bfc68e1) 42.16%.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #1171      +/-   ##
=============================================
+ Coverage      41.57%   42.16%   +0.58%     
- Complexity      3184     3226      +42     
=============================================
  Files            810      812       +2     
  Lines          17826    17917      +91     
  Branches        1938     1948      +10     
=============================================
+ Hits            7411     7554     +143     
+ Misses          9475     9415      -60     
- Partials         940      948       +8     

Flag	Coverage Δ
unittests	42.16% <68.96%> (+0.58%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ant/router/common/event/RouterEventDefinition.java	0.00% <0.00%> (ø)
...mant/router/common/event/RouterEventCollector.java	26.19% <12.50%> (+26.19%)	⬆️
.../sermant/router/config/utils/PolicyEventUtils.java	92.30% <92.30%> (ø)
...cloud/sermant/router/common/event/PolicyEvent.java	100.00% <100.00%> (ø)
...t/router/config/strategy/AbstractRuleStrategy.java	89.28% <100.00%> (+3.91%)	⬆️

... and 28 files with indirect coverage changes

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