New LOAD_ATTR_CLASS_WITH_METACLASS_CHECK does not guard against __class__ reassignment

Bug description:

This was found by Codex. Consider the following:

import enum
import _testinternalcapi

class ColorMeta(enum.EnumType):
    pass

class Color(enum.IntEnum, metaclass=ColorMeta):
    RED = 1

red = Color.RED

class Descriptor(enum.IntEnum):
    RED = 1

    def __get__(self, obj, owner):
        return "descr"

def get_enum_member():
    return Color.RED

for _ in range(_testinternalcapi.SPECIALIZATION_THRESHOLD):
    assert get_enum_member() == 1

red.__class__ = Descriptor

for _ in range(_testinternalcapi.SPECIALIZATION_THRESHOLD):
    assert get_enum_member() == "descr"

This passes without specializing interpreter, but fails with. @kumaraditya303

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-149269

首先分别在启用和不启用解释器特化的情况下运行 issue 的复现程序，重点关注 LOAD_ATTR_CLASS_WITH_METACLASS_CHECK 和 class 的重新赋值。将行为与链接的 PR gh-149269 进行比较；完成的标准是，重新赋值后，特化和非特化运行都返回描述符结果。