Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/wsgiref/util.pyi

@@ -0,0 +1,23 @@
+import sys
+from typing import IO, Any, Callable, Optional
+
+from .types import WSGIEnvironment
+
+class FileWrapper:
+    filelike: IO[bytes]
+    blksize: int
+    close: Callable[[], None]  # only exists if filelike.close exists
+    def __init__(self, filelike: IO[bytes], blksize: int = ...) -> None: ...
+    def __getitem__(self, key: Any) -> bytes: ...
+    def __iter__(self) -> FileWrapper: ...
+    if sys.version_info < (3,):
+        def next(self) -> bytes: ...
+    else:
+        def __next__(self) -> bytes: ...
+
+def guess_scheme(environ: WSGIEnvironment) -> str: ...
+def application_uri(environ: WSGIEnvironment) -> str: ...
+def request_uri(environ: WSGIEnvironment, include_query: bool = ...) -> str: ...
+def shift_path_info(environ: WSGIEnvironment) -> Optional[str]: ...
+def setup_testing_defaults(environ: WSGIEnvironment) -> None: ...
+def is_hop_by_hop(header_name: str) -> bool: ...