Add a Macro Benchmark that Exercises Threading (Multi-Core Concurrency)

From @methane (https://mail.python.org/archives/list/python-dev@python.org/message/KVH7QLJ4VJBQQ45LZTWDXO2SEC6ANX7T/):

CPU cache invalidation exists regardless. With the current GIL the
effect it is reduced significantly.

It's an interesting point. We can not see the benefit from pypeformance, because it doesn't use much data and it runs one process
at a time. So the pyperformance can not make enough stress to the last level cache which is shared by many cores.

We need multiprocess performance benchmark apart from pyperformance, to stress the last level cache from multiple cores. It helps not only this PEP, but also optimizing containers like dict and set.

Comienza revisando la suite de benchmarks existente de pyperformance y cómo están organizados sus benchmarks de un solo proceso. Define cómo un benchmark de multiprocessing debe ejercer presión sobre la caché de último nivel compartida entre los núcleos, y considera completo el benchmark cuando proporcione datos de rendimiento multinúcleo reproducibles que sean útiles para evaluar optimizaciones de dict y set.