Use ParamSpec for *GeneratorContextManager in contextlib

[sobolevn]

Source: https://github.com/python/cpython/blob/d45cd2d20770f72a000ba6dfa9ac88dd49423c27/Lib/contextlib.py#L105

[sobolevn]

We can also make it generic on _P, but I don't think it is worth it.

[AlexWaygood]

I already tried this :(

• Add missing attributes to contextlib._(Async)GeneratorContextManager #6676
• Add ParamSpec to contextlib._(Async)GeneratorContextManager #6775

[sobolevn]

Oh 🤔
I didn't know that code like

def (self, func: Callable[_P, Iterator[_T_co]], args: _P.args, kwds: _P.kwargs)

is not allowed. Only *args and **kwds.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

pyinstrument (https://github.com/joerick/pyinstrument)
- pyinstrument/vendor/decorator.py:295: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[_GeneratorContextManager[_T_co], Callable[..., Iterator[_T_co]], Tuple[Any, ...], Dict[str, Any]], None]")
+ pyinstrument/vendor/decorator.py:295: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[_GeneratorContextManager[_T_co], Callable[_P, Iterator[_T_co]], Any, Any], None]")
- pyinstrument/vendor/decorator.py:301: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[_GeneratorContextManager[_T_co], Callable[..., Iterator[_T_co]], Tuple[Any, ...], Dict[str, Any]], None]")
+ pyinstrument/vendor/decorator.py:301: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[_GeneratorContextManager[_T_co], Callable[_P, Iterator[_T_co]], Any, Any], None]")