`has no attribute "__aiter__"; maybe "__enter__"? (not async iterable)` when async iterating

Bug Report

On mypy 1.9.0, this code suggests, somewhat nonsensically, __enter__ because __aiter__ does not exist despite the reference to __aiter__ being entirely implicit in the async for loop:

from typing import Self

class Foo:
    def __enter__(self) -> Self:
        return self

async def f() -> None:
    async for x in Foo():
        print(x)

On playground: https://mypy-play.net/?mypy=latest&python=3.12&gist=3971471bd809ed97a72a1423a56f5318

Expected Behavior

Since the user did not type __aiter__, it is unlikely that it would be a typo for __enter__; therefore, probably the most helpful course would be to not give that suggestion.

Start by reproducing the diagnostic with the Python example in the issue and compare it with the linked mypy playground result. Trace the async-for error and suggestion handling, then verify that an implicit aiter reference no longer suggests enter; the corrected diagnostic should still explain that Foo is not asynchronously iterable.