[enh] Better reach %CPU configuration

proof.ts now relies on a CPU profiler, which allows for nearly perfect respect of the CPU% configuration.

Works very well both with ARM and Intel. Thus, the specific code for ARM has been removed from Duniter. The CPU% is now a generic configuration which works on every platform.

About reduce_cpu

This code don't interfere with @vincentrou 's code, except that the number of tests/second now takes into account the number of cores.

So if the lower limit to reach with ecomode = true is 300, then it will 300 for the whole machine (not 300 per core).

About speed

I could notice a slight improvement in unit tests (few seconds).