Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/msilib/text.pyi

@@ -0,0 +1,9 @@
+import sys
+from typing import List, Optional, Tuple
+
+if sys.platform == "win32":
+
+    ActionText: List[Tuple[str, str, Optional[str]]]
+    UIText: List[Tuple[str, Optional[str]]]
+
+    tables: List[str]