Improve CPU usage of main process by sleeping while going through child processes

The main process now consumes more than 80% of one CPU, when in the while loop of `Runner::run`
Having the main process sleep for 10 ms significantly significantly decreases the CPU usage of the main process.
From tests on my dev machine, If the process sleeps for 2-3 ms, the process still consumes more than 50% of the CPU.
Also having it sleep for more than 100ms significantly delays the total time.
Thus the somehow arbitrary 10ms.