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

Empieza por stdlib/functools.pyi alrededor de la línea 75 y revisa los conceptos ParamSpec y Concatenate de PEP 612. Comprueba la dependencia del issue #8708 y del issue relacionado de mypy antes de decidir si la tipificación solicitada puede expresarse. Se considera terminado cuando call de functools.partial conserva la tipificación de los parámetros del callable envuelto en lugar de usar Any.