Improve stubs for classmethod and staticmethod

[AlexWaygood]

Fixes #10396

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

ibis (https://github.com/ibis-project/ibis)
+ ibis/common/grounds.py:30: error: Need type annotation for "__create__"  [var-annotated]
- ibis/common/grounds.py:93: note:          classmethod[type, [VarArg(Any), KwArg(Any)], Any]
+ ibis/common/grounds.py:93: note:          classmethod[Any, [VarArg(Any), KwArg(Any)], Any]
- ibis/common/grounds.py:96: error: Argument 1 to "__get__" of "classmethod" has incompatible type "None"; expected "type"  [arg-type]
- ibis/common/grounds.py:96: error: Argument 2 to "__get__" of "classmethod" has incompatible type "type[Annotable]"; expected "type[type] | None"  [arg-type]
- ibis/common/grounds.py:102: error: Argument 1 to "__get__" of "classmethod" has incompatible type "None"; expected "type"  [arg-type]
- ibis/common/grounds.py:102: error: Argument 2 to "__get__" of "classmethod" has incompatible type "type[Annotable]"; expected "type[type] | None"  [arg-type]
- ibis/common/grounds.py:175: note:          classmethod[type, [VarArg(Any), KwArg(Any)], Any]
+ ibis/common/grounds.py:175: note:          classmethod[Any, [VarArg(Any), KwArg(Any)], Any]
- ibis/common/grounds.py:180: error: Argument 1 to "__get__" of "classmethod" has incompatible type "None"; expected "type"  [arg-type]
- ibis/common/grounds.py:180: error: Argument 2 to "__get__" of "classmethod" has incompatible type "type[Singleton]"; expected "type[type] | None"  [arg-type]

prefect (https://github.com/PrefectHQ/prefect)
- src/prefect/results.py:400: note:          abstractclassmethod[type[BaseResult[R]], [R, KwArg(Any)], Coroutine[Any, Any, BaseResult[R]]]
+ src/prefect/results.py:400: note:          abstractclassmethod[BaseResult[R], [R, KwArg(Any)], Coroutine[Any, Any, BaseResult[R]]]
- src/prefect/results.py:437: note:          abstractclassmethod[type[BaseResult[R]], [R, KwArg(Any)], Coroutine[Any, Any, BaseResult[R]]]
+ src/prefect/results.py:437: note:          abstractclassmethod[BaseResult[R], [R, KwArg(Any)], Coroutine[Any, Any, BaseResult[R]]]
- src/prefect/results.py:509: note:          abstractclassmethod[type[BaseResult[R]], [R, KwArg(Any)], Coroutine[Any, Any, BaseResult[R]]]
+ src/prefect/results.py:509: note:          abstractclassmethod[BaseResult[R], [R, KwArg(Any)], Coroutine[Any, Any, BaseResult[R]]]

steam.py (https://github.com/Gobot1234/steam.py)
+ steam/id.py:274: error: Need type annotation for "__class_getitem__"  [var-annotated]

[AlexWaygood]

Looks like this gets rid of a few false-positive errors in ibis.