fix: add weakref.proxy stuff to testdata stubs

Author: BobTheBuidler

test-data/unit/lib-stub/weakref.pyi

@@ -1,11 +1,25 @@
 from collections.abc import Callable
-from typing import Any, Generic, TypeVar
+from typing import Any, ClassVar, Generic, TypeVar, final, overload
 from typing_extensions import Self
 
+_C = TypeVar("_C", bound=Callable[..., Any])
 _T = TypeVar("_T")
 
 class ReferenceType(Generic[_T]):  # "weakref"
     __callback__: Callable[[Self], Any]
     def __new__(cls, o: _T, callback: Callable[[Self], Any] | None = ..., /) -> Self: ...
 
 ref = ReferenceType
+
+@final
+class CallableProxyType(Generic[_C]):  # "weakcallableproxy"
+    def __eq__(self, value: object, /) -> bool: ...
+    def __getattr__(self, attr: str) -> Any: ...
+    __call__: _C
+    __hash__: ClassVar[None]  # type: ignore[assignment]
+
+# Return CallableProxyType if object is callable, ProxyType otherwise
+@overload
+def proxy(object: _C, callback: Callable[[_C], Any] | None = None, /) -> CallableProxyType[_C]: ...
+@overload
+def proxy(object: _T, callback: Callable[[_T], Any] | None = None, /) -> Any: ...