General Design for Metrics(memory、cpu...) adaptive flow control

[louyuting]

Issue Description

Type: feature request

Describe what feature you want

Additional context

refer to #348
Add any other context or screenshots about the feature request here.

[liqiangz]

自适应模块抽象方案

1.新建 adaptive 模块，可以做一些 ratio 相关的 adjustment.

type AdaptiveConfig struct {
	//用户自定义名称
	AdaptiveConfigName string
	//自适应类型，cpu、mem...
	AdaptiveType  AdaptiveType
	
	//相应自适应类型所需要的参数
	LowRatio      float64
	HighRatio     float64
	LowWaterMark  float64
	HighWaterMark float64
}

// 根据用户配置生成的 AdaptiveController
type AdaptiveController interface {
        //根据用户配置的系统自适应规则来做adjustment
	CalculateSystemAdaptiveCount(count float64) float64
}

var adaptiveControllerMap map[string]*AdaptiveController

//获取指定的 AdaptiveController
func GetAdaptiveController(adaptiveName string) *AdaptiveController {
}

//加载自适应配置
func LoadAdaptiveConfig(configs []*AdaptiveConfig) (bool, error){
}

2. flow模块修改

//添加字段 AdaptiveConfigName,用于指定配置的自适应规则
type Rule struct {
...
AdaptiveConfigName string
...
}

//修改 DirectTrafficShapingCalculator 如下, 目前自适应仅支持 Direct 的 Token 计算策略
func (d *DirectTrafficShapingCalculator) CalculateAllowedTokens(uint32, int32) float64 {
	if d.owner.rule.AdaptiveConfigName != ""{
		 ac := adaptive.GetAdaptiveController(d.owner.rule.AdaptiveConfigName)
                 if ac != nil {
                    return ac.CalculateSystemAdaptiveCount(d.threshold)
                 }
	}
	return d.threshold
}

[louyuting]

It's basically OK to me