Add inspection for cgroup v2 CPU quota and period

I see this function, and essentially, I want to somehow use it in a Go application that runs inside a cpu-limited container so the app can understand its environment better:

https://github.com/containerd/cgroups/blob/f1e92d84a45c1c1ae283505f5b680156687ef2f0/cgroup2/cpu.go#L56

https://github.com/containerd/cgroups/blob/f1e92d84a45c1c1ae283505f5b680156687ef2f0/cgroup2/manager.go#L953

I don't see any way to get at this information from the current public API.

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Is this something that would make sense to include in this module? The readme says "inspecting" cgroups is one of its goals, so my guess is that it would be a good feature.