gating:Deprecate cgroup v1, change CPU-measurements to cgroup level

We have been failing to measure the CPU used under child processes, due to a lacking caveat of psutil.Process.cpu_times. The used CPU of children, are only ever incremented at time of wait reaping a terminated child process.

This means that all actual CPU of processes running, either spawned itself or using the subprocess_middleware have not been accurately measured, breaking the CPU gating method.