[Fixes #1770]add statIntervalMs input in degrade-rule-dialog.html

[xierunzi]

#1770

Describe what this PR does / why we need it

add statIntervalMs input in degrade-rule-dialog.html

Does this pull request fix one issue?

fixes #1770

Describe how you did it

add an input.

Describe how to verify it

submit the button of add rule, the 'statIntervalMs' param in requests has been set to the input value.

Special notes for reviews

[sczyh30]

Any other suggestions? @cdfive

[cdfive]

LGTM

[cdfive]

@xierunzi @sczyh30 抱歉最近工作有点忙来晚了哈。
我对控制台自带的这个接口http://localhost:8080/version进行了测试，代码里增加了随机抛异常：

@GetMapping("/version")
public Result<String> apiGetVersion() {
  if (ThreadLocalRandom.current().nextBoolean()) {
    throw new RuntimeException("test version exception");
  }
...
}

目前切换熔断策略的单选按钮时，仅第3行有改变，界面没有大的晃动看上去更直观了。
设置了不同统计时长、异常数、最小请求数进行测试，经测试设置该值有效，宿何再看看帮合下哈。
感谢参与贡献！@xierunzi

[sczyh30]

Thanks for contributing and look forward to more!