Improve stubtest handling of expected dunder methods

[AlexWaygood]

Stubtest currently suppresses diagnostics regarding missing dunder methods whenever the runtime attribute is a WrapperDescriptorType. This is because WrapperDescriptorType dunders are often not actually callable at runtime, so suppressing these diagnostics avoids many false positives. However, it also hides genuine omissions such as collections.deque.__rmul__ (typeshed#16055).

This PR keeps the existing suppression in the general case while reporting missing methods that the stub gives us a reason to expect:

• If a stub class has a __add__ method, a diagnostic regarding a missing __radd__ method is probably not a false positive
• If a a stub class has a __lt__ method, a diagnostic regarding a missing __gt__ method is probably not a false positive
• If a stub class inherits from Mapping, diagnostics regarding missing __or__, __ror__ or __ior__ are probably not false positives
• If a stub class inherits from Sequence, diagnostics regarding missing __mul__, __rmul__ or __imul__ methods are probably not false positives.

There may be more heuristics we could add similar to these. These were just the ones I/Codex could think of.

[AlexWaygood]

This patch produces 17 new hits on typeshed's stdlib on Python 3.10–3.14, with three additional hits on Python 3.15. None are currently allowlisted.

builtins.bytearray.__rmod__
builtins.bytes.__rmod__
builtins.frozenset.__rand__
builtins.frozenset.__ror__
builtins.frozenset.__rsub__
builtins.frozenset.__rxor__
builtins.set.__rand__
builtins.set.__ror__
builtins.set.__rsub__
builtins.set.__rxor__
builtins.str.__rmod__
datetime.date.__rsub__
datetime.datetime.__rsub__
datetime.timedelta.__rdivmod__
datetime.timedelta.__rfloordiv__
datetime.timedelta.__rmod__
datetime.timedelta.__rtruediv__

Python 3.15 only:

types.FrameLocalsProxyType.__ior__
types.FrameLocalsProxyType.__or__
types.FrameLocalsProxyType.__ror__

These all appear to be true positives that we should probably fix in typeshed.

Codex analysis of the new hits

All 20 are callable wrapper_descriptors. Here are direct runtime examples. For reflected methods, the first argument is the receiver/right-hand operand and the second represents the left-hand operand.

>>> str.__rmod__("world", "hello %s")
'hello world'
>>> bytes.__rmod__(b"world", b"hello %s")
b'hello world'
>>> bytearray.__rmod__(bytearray(b"world"), bytearray(b"hello %s"))
bytearray(b'hello world')

>>> set.__rand__({2, 3}, {1, 2})
{2}
>>> set.__ror__({2, 3}, {1, 2})
{1, 2, 3}
>>> set.__rsub__({2, 3}, {1, 2})
{1}
>>> set.__rxor__({2, 3}, {1, 2})
{1, 3}

>>> frozenset.__rand__(frozenset({2, 3}), frozenset({1, 2}))
frozenset({2})
>>> frozenset.__ror__(frozenset({2, 3}), frozenset({1, 2}))
frozenset({1, 2, 3})
>>> frozenset.__rsub__(frozenset({2, 3}), frozenset({1, 2}))
frozenset({1})
>>> frozenset.__rxor__(frozenset({2, 3}), frozenset({1, 2}))
frozenset({1, 3})

>>> from datetime import date, datetime, timedelta
>>> date.__rsub__(date(2025, 1, 1), date(2025, 1, 4))
datetime.timedelta(days=3)
>>> datetime.__rsub__(datetime(2025, 1, 1), datetime(2025, 1, 4))
datetime.timedelta(days=3)
>>> timedelta.__rdivmod__(timedelta(days=2), timedelta(days=7))
(3, datetime.timedelta(days=1))
>>> timedelta.__rfloordiv__(timedelta(days=2), timedelta(days=7))
3
>>> timedelta.__rmod__(timedelta(days=2), timedelta(days=7))
datetime.timedelta(days=1)
>>> timedelta.__rtruediv__(timedelta(days=2), timedelta(days=7))
3.5

The three Python 3.15-specific hits are also callable:

>>> import sys
>>> import types
>>> def get_frame():
...     value = 1
...     return sys._getframe()
...
>>> frame = get_frame()
>>> locals_proxy = frame.f_locals
>>> types.FrameLocalsProxyType.__or__(locals_proxy, {"other": 2})
{'value': 1, 'other': 2}
>>> types.FrameLocalsProxyType.__ror__(locals_proxy, {"other": 2})
{'other': 2, 'value': 1}
>>> types.FrameLocalsProxyType.__ior__(locals_proxy, {"other": 2})
{'value': 1, 'other': 2}
>>> frame.f_locals
{'value': 1, 'other': 2}