Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/msilib/sequence.pyi

@@ -0,0 +1,14 @@
+import sys
+from typing import List, Optional, Tuple
+
+if sys.platform == "win32":
+
+    _SequenceType = List[Tuple[str, Optional[str], int]]
+
+    AdminExecuteSequence: _SequenceType
+    AdminUISequence: _SequenceType
+    AdvtExecuteSequence: _SequenceType
+    InstallExecuteSequence: _SequenceType
+    InstallUISequence: _SequenceType
+
+    tables: List[str]