Update _asyncio to 3.14 (#14165)

stdlib/_asyncio.pyi

@@ -107,3 +107,4 @@ if sys.version_info >= (3, 12):
 if sys.version_info >= (3, 14):
     def future_discard_from_awaited_by(future: Future[Any], waiter: Future[Any], /) -> None: ...
     def future_add_to_awaited_by(future: Future[Any], waiter: Future[Any], /) -> None: ...
+    def all_tasks(loop: AbstractEventLoop | None = None) -> set[Task[Any]]: ...