[question]CgroupRoot 是做什么用的，和其他ResourceQOS 有啥关系，难道ResourceQOS 都是通过cgroup实现的么？

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What happened:

type ResourceQOSStrategy struct {
	// Policies of pod QoS.
	Policies *ResourceQOSPolicies `json:"policies,omitempty"`

	// ResourceQOS for LSR pods.
	LSRClass *ResourceQOS `json:"lsrClass,omitempty"`

	// ResourceQOS for LS pods.
	LSClass *ResourceQOS `json:"lsClass,omitempty"`

	// ResourceQOS for BE pods.
	BEClass *ResourceQOS `json:"beClass,omitempty"`

	// ResourceQOS for system pods
	SystemClass *ResourceQOS `json:"systemClass,omitempty"`

	// ResourceQOS for root cgroup.
	CgroupRoot *ResourceQOS `json:"cgroupRoot,omitempty"`
}

What you expected to happen:

Environment:

• Koordinator version: - v0.6.2
• Kubernetes version (use kubectl version): v1.22.5
• docker/containerd version: containerd 1.5.0
• OS (e.g: cat /etc/os-release): Ubuntu 20.04.4 LTS
• Kernel (e.g. uname -a): Linux 5.10.112-11.al8.x86_64 ✨ Add NodeMetric API #1 SMP Tue May 24 16:05:50 CST 2022 x86_64 x86_64 x86_64 GNU/Linux

Anything else we need to know: