Add overloads to unittest.mock._patch_dict.__call__

[mxr]

Resolves #16307

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[AlexWaygood]

it's not totally clear to me how having three overloads here is any different to doing this:

Suggested change

	@overload
	def __call__(self, f: _TT) -> _TT: ...
	@overload
	def __call__(self, f: _AF) -> _AF: ...
	@overload
	def __call__(self, f: _F) -> _F: ...
	def __call__(self, f: _F) -> _F: ...

Any type assignable to type[Any] (upper bound of _TT) or Callable[..., Coroutine[Any, Any, Any]](upper bound of _AF) will also be assignable to Callable[..., Any] (upper bound of _F), and a type checker will always pick the most precise type when solving a generic call

[AlexWaygood]

I dug through the blame a bit to see if there had been any previous churn or discussion about this signature, since annotations in unittest.mock have caused us some level of difficulty in the past... it looks like this has been unchanged since 2017! Type annotations were added in #973

[AlexWaygood]

This LGTM other than the simplification I suggested above, it does seem like this preserves the wrapped function's signature. Thanks!