Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/multiprocessing/queues.pyi

@@ -0,0 +1,35 @@
+import queue
+import sys
+from typing import Any, Generic, Optional, TypeVar
+
+if sys.version_info >= (3, 9):
+    from types import GenericAlias
+
+_T = TypeVar("_T")
+
+class Queue(queue.Queue[_T]):
+    # FIXME: `ctx` is a circular dependency and it's not actually optional.
+    # It's marked as such to be able to use the generic Queue in __init__.pyi.
+    def __init__(self, maxsize: int = ..., *, ctx: Any = ...) -> None: ...
+    def get(self, block: bool = ..., timeout: Optional[float] = ...) -> _T: ...
+    def put(self, obj: _T, block: bool = ..., timeout: Optional[float] = ...) -> None: ...
+    def qsize(self) -> int: ...
+    def empty(self) -> bool: ...
+    def full(self) -> bool: ...
+    def put_nowait(self, item: _T) -> None: ...
+    def get_nowait(self) -> _T: ...
+    def close(self) -> None: ...
+    def join_thread(self) -> None: ...
+    def cancel_join_thread(self) -> None: ...
+
+class JoinableQueue(Queue[_T]):
+    def task_done(self) -> None: ...
+    def join(self) -> None: ...
+
+class SimpleQueue(Generic[_T]):
+    def __init__(self, *, ctx: Any = ...) -> None: ...
+    def empty(self) -> bool: ...
+    def get(self) -> _T: ...
+    def put(self, item: _T) -> None: ...
+    if sys.version_info >= (3, 9):
+        def __class_getitem__(cls, item: Any) -> GenericAlias: ...