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.

先檢視現有的 pyperformance 基準測試套件，以及其中的單一程序基準測試是如何組織的。定義多程序基準測試應如何在各核心之間施加共享的末級快取壓力，並在該基準測試能提供可重現的多核心效能資料、可用於評估 dict 和 set 最佳化時，將其視為完成。