Add a few missing dunders in builtins (#7214)

Author: AlexWaygood

stdlib/builtins.pyi

@@ -660,6 +660,7 @@ class bytearray(MutableSequence[int], ByteString):
     def __le__(self, __x: bytes) -> bool: ...
     def __gt__(self, __x: bytes) -> bool: ...
     def __ge__(self, __x: bytes) -> bool: ...
+    def __alloc__(self) -> int: ...
 
 @final
 class memoryview(Sized, Sequence[int]):
@@ -998,6 +999,7 @@ class property:
     fget: Callable[[Any], Any] | None
     fset: Callable[[Any, Any], None] | None
     fdel: Callable[[Any], None] | None
+    __isabstractmethod__: bool
     def __init__(
         self,
         fget: Callable[[Any], Any] | None = ...,
@@ -1420,6 +1422,7 @@ class reversed(Iterator[_T], Generic[_T]):
     def __init__(self, __sequence: SupportsLenAndGetItem[_T]) -> None: ...
     def __iter__(self: Self) -> Self: ...
     def __next__(self) -> _T: ...
+    def __length_hint__(self) -> int: ...
 
 def repr(__obj: object) -> str: ...
 @overload