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.

首先查看现有的 pyperformance 基准测试套件，以及其中的单进程基准测试是如何组织的。明确多进程基准测试应如何在各核心之间施加共享末级缓存压力，并在该基准测试能够提供可复现的多核性能数据、可用于评估 dict 和 set 优化时，认为它已完成。