a couple stubtest fixes in multiprocessing (#12948)

Author: tungol

stdlib/@tests/stubtest_allowlists/common.txt

@@ -74,15 +74,13 @@ ipaddress._BaseNetwork.max_prefixlen
 multiprocessing.JoinableQueue
 multiprocessing.Queue
 multiprocessing.SimpleQueue
-multiprocessing.managers.BaseManager.shutdown
 multiprocessing.managers.SyncManager.Event
 multiprocessing.managers.SyncManager.Lock
 multiprocessing.managers.SyncManager.Namespace
 multiprocessing.managers.SyncManager.RLock
 multiprocessing.queues.JoinableQueue.__init__
 multiprocessing.queues.Queue.__init__
 multiprocessing.queues.SimpleQueue.__init__
-multiprocessing.spawn._main
 multiprocessing.synchronize.Barrier.__init__
 multiprocessing.synchronize.Condition.acquire
 multiprocessing.synchronize.Condition.release

stdlib/multiprocessing/managers.pyi

@@ -10,6 +10,7 @@ from typing_extensions import Self, TypeAlias
 from .connection import Connection
 from .context import BaseContext
 from .shared_memory import _SLT, ShareableList as _ShareableList, SharedMemory as _SharedMemory
+from .util import Finalize as _Finalize
 
 __all__ = ["BaseManager", "SyncManager", "BaseProxy", "Token", "SharedMemoryManager"]
 
@@ -156,7 +157,7 @@ class BaseManager:
     def get_server(self) -> Server: ...
     def connect(self) -> None: ...
     def start(self, initializer: Callable[..., object] | None = None, initargs: Iterable[Any] = ()) -> None: ...
-    def shutdown(self) -> None: ...  # only available after start() was called
+    shutdown: _Finalize  # only available after start() was called
     def join(self, timeout: float | None = None) -> None: ...  # undocumented
     @property
     def address(self) -> Any: ...

stdlib/multiprocessing/spawn.pyi

@@ -23,7 +23,7 @@ def get_command_line(**kwds: Any) -> list[str]: ...
 def spawn_main(pipe_handle: int, parent_pid: int | None = None, tracker_fd: int | None = None) -> None: ...
 
 # undocumented
-def _main(fd: int) -> Any: ...
+def _main(fd: int, parent_sentinel: int) -> int: ...
 def get_preparation_data(name: str) -> dict[str, Any]: ...
 
 old_main_modules: list[ModuleType]