functools.partial should use PEP612 ParamSpec (depends on #8708)

Currently, functools.partial's __call__ method takes *args: Any, **kwargs: Any and returns _T (a TypeVar for the return type of the callable the partial is wrapping). This is decent, but matching the parameter typing would make this more useful in more situations.

I can sort of see how to deal with this, although I'll admit I'm unsure how to make this generically work. I imagine you could probably deal with some number of Concatenates (maybe up to 5 or 10) to deal with most cases. It's possible fixing this requires another PEP to allow an arbitrary-length Concatenate-type pattern.

Related to https://github.com/python/mypy/issues/1484

从 stdlib/functools.pyi 第 75 行附近开始，并审查 PEP 612 的 ParamSpec 和 Concatenate 概念。在决定所请求的类型标注是否可以表达之前，检查对 issue #8708 以及相关 mypy issue 的依赖。完成的标准是 functools.partial 的 call 保留被包装 callable 的参数类型标注，而不是使用 Any。