Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/tkinter/dialog.pyi

@@ -0,0 +1,10 @@
+from tkinter import Widget
+from typing import Any, Mapping, Optional
+
+DIALOG_ICON: str
+
+class Dialog(Widget):
+    widgetName: str = ...
+    num: int = ...
+    def __init__(self, master: Optional[Any] = ..., cnf: Mapping[str, Any] = ..., **kw) -> None: ...
+    def destroy(self) -> None: ...