aiofiles: add type for executor parameter (#14226)

Fix partially unknown executor

stubs/aiofiles/aiofiles/threadpool/__init__.pyi

@@ -8,6 +8,7 @@ from _typeshed import (
 )
 from asyncio import AbstractEventLoop
 from collections.abc import Callable
+from concurrent.futures import Executor
 from typing import Literal, overload
 from typing_extensions import TypeAlias
 
@@ -30,7 +31,7 @@ def open(
     opener: _Opener | None = None,
     *,
     loop: AbstractEventLoop | None = None,
-    executor=None,
+    executor: Executor | None = None,
 ) -> AiofilesContextManager[AsyncTextIOWrapper]: ...
 
 # Unbuffered binary: returns a FileIO
@@ -46,7 +47,7 @@ def open(
     opener: _Opener | None = None,
     *,
     loop: AbstractEventLoop | None = None,
-    executor=None,
+    executor: Executor | None = None,
 ) -> AiofilesContextManager[AsyncFileIO]: ...
 
 # Buffered binary reading/updating: AsyncBufferedReader
@@ -62,7 +63,7 @@ def open(
     opener: _Opener | None = None,
     *,
     loop: AbstractEventLoop | None = None,
-    executor=None,
+    executor: Executor | None = None,
 ) -> AiofilesContextManager[AsyncBufferedReader]: ...
 
 # Buffered binary writing: AsyncBufferedIOBase
@@ -78,7 +79,7 @@ def open(
     opener: _Opener | None = None,
     *,
     loop: AbstractEventLoop | None = None,
-    executor=None,
+    executor: Executor | None = None,
 ) -> AiofilesContextManager[AsyncBufferedIOBase]: ...
 
 # Buffering cannot be determined: fall back to _UnknownAsyncBinaryIO
@@ -94,7 +95,7 @@ def open(
     opener: _Opener | None = None,
     *,
     loop: AbstractEventLoop | None = None,
-    executor=None,
+    executor: Executor | None = None,
 ) -> AiofilesContextManager[_UnknownAsyncBinaryIO]: ...
 
 stdin: AsyncTextIndirectIOWrapper