`[Async]ContextDecorator.__call__` return type should depend on the underlying context manager's `_ExitT_co`

[!Important]
Please see https://discuss.python.org/t/support-suppressing-generator-context-managers/103615 first!

This is how ContextDecorator.__call__ is implemented in the Python standard library:

def __call__(self, func):
    @wraps(func)
    def inner(*args, **kwds):
        with self._recreate_cm():
            return func(*args, **kwds)
    return inner

In typeshed, ContextDecorator.__call__ currently has a return type of the original callable (func).
However, if the return value of self._recreate_cm().__call__ is truthy, the return type of ContextDecorator.__call__ can as well be None, like in the silly example below:

from collections.abc import Generator
from contextlib import contextmanager, suppress
from typing import reveal_type


@contextmanager
def zero_division_to_none() -> Generator[None]:
    with suppress(ZeroDivisionError):
        yield


@zero_division_to_none()
def div(a: int, b: int) -> float:
    return a / b


reveal_type(div(1, 0))
# mypy, pyright: Revealed type is "builtins.float"
# Runtime type is 'NoneType'

My first shot was to patch the proper __call__ functions to "extend" the return type with _ThrottledExcReturnT (a new type parameter of ContextDecorator), constrained by Never and None, with the default type Never for backward compatibility. To me, there's no way to declare the relationship symbolically, so it would have to be typed manually in classes implementing the context manager protocol.

Beginnen Sie mit der verlinkten Python-Diskussion und der Implementierung der Standardbibliothek in Lib/contextlib.py, wobei Sie sich auf ContextDecorator.call und den zugrunde liegenden _ExitT_co des Context Managers konzentrieren. Ermitteln Sie eine unterstützte Beziehung auf Typebene für den Rückgabetyp der umschlossenen aufrufbaren Funktion und überprüfen Sie anschließend, dass die Annotation Fälle widerspiegelt, in denen die Unterdrückung durch den Context Manager None zurückgibt.