bpo-33906: Rename idlelib.windows as window (GH-7833)


Match Window on the main menu and remove last plural module name.
Change imports, test, and attribute references to match new name.
(cherry picked from commit a361e89d5ae3daefe9e8b8a7e889cd2ad8c45b77)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
diff --git a/Lib/idlelib/macosx.py b/Lib/idlelib/macosx.py
index d85278a..3d29612 100644
--- a/Lib/idlelib/macosx.py
+++ b/Lib/idlelib/macosx.py
@@ -128,7 +128,7 @@
     # menu.
     from tkinter import Menu
     from idlelib import mainmenu
-    from idlelib import windows
+    from idlelib import window
 
     closeItem = mainmenu.menudefs[0][1][-2]