Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/@python2/runpy.pyi

@@ -0,0 +1,17 @@
+from typing import Any, Optional
+
+class _TempModule:
+    mod_name: Any
+    module: Any
+    def __init__(self, mod_name): ...
+    def __enter__(self): ...
+    def __exit__(self, *args): ...
+
+class _ModifiedArgv0:
+    value: Any
+    def __init__(self, value): ...
+    def __enter__(self): ...
+    def __exit__(self, *args): ...
+
+def run_module(mod_name, init_globals: Optional[Any] = ..., run_name: Optional[Any] = ..., alter_sys: bool = ...): ...
+def run_path(path_name, init_globals: Optional[Any] = ..., run_name: Optional[Any] = ...): ...