Revert "Improve [Async]ContextDecorator type hinting (#13416)"

[ncoghlan]

This reverts commit 57d7c43.

The attempted fix loses all type overload information during type inferencing, so postpone fixing the issue until we have a solution which doesn't impose such a dramatic loss in functionality.

Reopens #13403

[github-actions]

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

jax (https://github.com/google/jax)
- jax/_src/api.py:2671: error: Incompatible return value type (got "_WrappedCallable[[VarArg(Any), KwArg(Any)], Any]", expected "F")  [return-value]
- jax/experimental/jax2tf/jax2tf.py:3059: error: Argument 1 has incompatible type "_GeneratorContextManager[NameStack, None, None]"; expected "Callable[[partial[Sequence[Any]]], partial[Sequence[Any]]]"  [arg-type]
- jax/experimental/jax2tf/jax2tf.py:3059: note: "_GeneratorContextManager[NameStack, None, None].__call__" has type "Callable[[Arg(Callable[_P, _R], 'func')], _WrappedCallable[_P, _R]]"

cki-lib (https://gitlab.com/cki-project/cki-lib)
+ tests/test_metrics.py:75: error: Call to untyped function "dummy_function" in typed context  [no-untyped-call]

[ncoghlan]

Discourse thread with background on this: https://discuss.python.org/t/defining-overload-preserving-signatures-for-wrapped-callables/78350

[cdce8p]

What is the current status here? We're currently holding off on a typeshed sync in Mypy to wait for a resolution here. See python/mypy#18580

[ncoghlan]

I'm not sure. When I submitted the initial change, I thought it was a simple bug fix, but it turned out it opened up a giant can of worms around whether or not type checkers should be keeping track of overload details when a parameter spec and result type pair are combined as a callable interface in a generic class definition.

[DetachHead]

this also breaks methods decorated with a @contextmanager:

from contextlib import contextmanager
from collections.abc import Generator


@contextmanager
def foo() -> Generator[None]: ...

asdf = foo()

class Foo:
    @foo()
    def bar(self):
        ...

Foo().bar() # Argument missing for parameter "self"  (reportCallIssue)

playground