[Experimental] Tracing GC (by Codex)

I participate in the Codex OSS Program, but I end up with a lot of unused AI credits every week. So I decided to have the latest model explore some ideas that I had been interested in but hadn’t been able to investigate due to my limited knowledge and time. This pull request replaces Python’s reference counting with a tracing GC and was then optimized over the course of several days. https://github.com/methane/cpython/pull/125 The results may not be particularly exciting. Python performs a la...