Wrong type inference for class with metaclass that acts as descriptor

Bug Report
Descriptor protocol does not work on metaclasses - defining __get__ method in a metaclass does not make classes using that metaclass work as descriptors.

To Reproduce

1. Put this code in a py file:

from typing import Any, TYPE_CHECKING, overload

class _IntDescriptorMeta(type):
    def __get__(self, instance: Any, owner: Any) -> int:
        return 123

class IntDescriptorClass(metaclass=_IntDescriptorMeta):
    ...

class IntDescriptor:
    def __get__(self, instance: Any, owner: Any) -> int:
        return 123

class X:
    number_cls = IntDescriptorClass
    number = IntDescriptor()

print(X.number_cls)
print(X().number_cls)
print(X.number)
print(X().number)

if TYPE_CHECKING:
    reveal_type(X.number_cls)
    reveal_type(X().number_cls)
    reveal_type(X.number)
    reveal_type(X().number)

2. Run it, you should see:

123
123
123
123

3. Type check it with mypy and see the incorrect output.

Expected Behavior
I expected mypy to infer type of X.number_cls/X().number_cls correctly:

main.py:24: note: Revealed type is "builtins.int"
main.py:25: note: Revealed type is "builtins.int"
main.py:26: note: Revealed type is "builtins.int"
main.py:27: note: Revealed type is "builtins.int"

Note:
To simplify this example, __get__ returns an int no matter if instance is None or not but I assume a fix would also make it work properly with overloads as it does for instances of classes.

Actual Behavior

Mypy does not infer type of X.number_cls/X().number_cls correctly:

main.py:24: note: Revealed type is "def () -> __main__.IntDescriptorClass"
main.py:25: note: Revealed type is "def () -> __main__.IntDescriptorClass"
main.py:26: note: Revealed type is "builtins.int"
main.py:27: note: Revealed type is "builtins.int"

Your Environment

• Mypy version used: 0.910 as well as the latest (master branch)
• mypy-play.net URL: https://mypy-play.net/?mypy=latest&python=3.8&gist=de23d753f19cf0149ed9cd6919e84791

Additional notes
This works properly on pyright 1.1.161+, see the issue: https://github.com/microsoft/pyright/issues/2164

Beginne damit, die bereitgestellte Python-Reproduktion auszuführen und die aufgedeckten Typen mit mypy zu prüfen; verwende bei Bedarf die verknüpfte mypy-play-URL. Verfolge mypys Typinferenz für Deskriptoren, die auf Metaklassen definiert sind, und vergleiche sie mit gewöhnlichen Instanzdeskriptoren. Als abgeschlossen gilt die Aufgabe, wenn alle vier Reveals für den klassenbasierten Deskriptor builtins.int melden und das bestehende Verhalten von Deskriptoren weiterhin korrekt ist.