Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/asyncio/subprocess.pyi

@@ -0,0 +1,60 @@
+import sys
+from asyncio import events, protocols, streams, transports
+from typing import IO, Any, Optional, Tuple, Union
+
+if sys.version_info >= (3, 8):
+    from os import PathLike
+
+    _ExecArg = Union[str, bytes, PathLike[str], PathLike[bytes]]
+else:
+    _ExecArg = Union[str, bytes]  # Union used instead of AnyStr due to mypy issue  #1236
+
+PIPE: int
+STDOUT: int
+DEVNULL: int
+
+class SubprocessStreamProtocol(streams.FlowControlMixin, protocols.SubprocessProtocol):
+    stdin: Optional[streams.StreamWriter]
+    stdout: Optional[streams.StreamReader]
+    stderr: Optional[streams.StreamReader]
+    def __init__(self, limit: int, loop: events.AbstractEventLoop) -> None: ...
+    def connection_made(self, transport: transports.BaseTransport) -> None: ...
+    def pipe_data_received(self, fd: int, data: Union[bytes, str]) -> None: ...
+    def pipe_connection_lost(self, fd: int, exc: Optional[Exception]) -> None: ...
+    def process_exited(self) -> None: ...
+
+class Process:
+    stdin: Optional[streams.StreamWriter]
+    stdout: Optional[streams.StreamReader]
+    stderr: Optional[streams.StreamReader]
+    pid: int
+    def __init__(
+        self, transport: transports.BaseTransport, protocol: protocols.BaseProtocol, loop: events.AbstractEventLoop
+    ) -> None: ...
+    @property
+    def returncode(self) -> Optional[int]: ...
+    async def wait(self) -> int: ...
+    def send_signal(self, signal: int) -> None: ...
+    def terminate(self) -> None: ...
+    def kill(self) -> None: ...
+    async def communicate(self, input: Optional[bytes] = ...) -> Tuple[bytes, bytes]: ...
+
+async def create_subprocess_shell(
+    cmd: Union[str, bytes],  # Union used instead of AnyStr due to mypy issue  #1236
+    stdin: Union[int, IO[Any], None] = ...,
+    stdout: Union[int, IO[Any], None] = ...,
+    stderr: Union[int, IO[Any], None] = ...,
+    loop: Optional[events.AbstractEventLoop] = ...,
+    limit: int = ...,
+    **kwds: Any,
+) -> Process: ...
+async def create_subprocess_exec(
+    program: _ExecArg,
+    *args: _ExecArg,
+    stdin: Union[int, IO[Any], None] = ...,
+    stdout: Union[int, IO[Any], None] = ...,
+    stderr: Union[int, IO[Any], None] = ...,
+    loop: Optional[events.AbstractEventLoop] = ...,
+    limit: int = ...,
+    **kwds: Any,
+) -> Process: ...