Type narrowing fails for classes with custom `__getattr__`

Bug Report

When a class has a custom __getattr__ with the return type of Any, the type narrowing of mypy does not work as expected in some cases.

To Reproduce

from typing import Any, Iterator, Union
from typing_extensions import reveal_type

class A(object):
    def __getattr__(self, name: str) -> Any:
        if name == "a":
            return 1
        else:
            raise AttributeError


def func(a: Union[A, Iterator[A]]) -> None:
    if isinstance(a, A):
        reveal_type(a)
    else:
        reveal_type(a)

Expected Behavior

Revealed type is "A"
Revealed type is "typing.Iterator[A]"

Actual Behavior

Revealed type is "A"
Revealed type is "Union[A, typing.Iterator[A]]"

Your Environment

• Mypy version used: mypy 1.6.1
• Mypy command-line flags: No flags were used.
• Mypy configuration options from mypy.ini (and other config files): None.
• Python version used: Python 3.10.13

Start by running the supplied Python reproducer with mypy 1.6.1 and comparing the revealed types with the expected output. Trace the type narrowing path for isinstance checks when the class defines getattr returning Any; done means the else branch narrows to Iterator[A] without regressing the first branch.