A function that returns a populated Resources struct

[iholder101]

The problem:
AFAICT, currently there is no way of getting a populated Resources struct from the cgroup manager.

This means that in order to understand the current configuration of a cgroup, there's a need to:

• Call manager.GetPaths().
• Iterate on the given paths for every different controller/subsystem.
• For every subsystem: read the different files, parse them, etc.

The above should be written in two versions to support both cgroup v1 and v2.

The solution:
I would expect that the manager would support a GetResources() function that returns a populated Resources struct. This seems like a very valuable action that has to be re-implemented in many different projects.

If this idea would be accepted, I'm willing to invest time in implementing it.

p.s. the manager.GetStats() method is not enough, since it can't, as a single example, get cpu.wight's value.

[lifubang]

Though we want to move most packages into internal, but I think ‘libct/cgroups’ is not included. So SGTM, please feel free to open a PR to implement this.