Previously, checkbuttons in different parent widgets could have the same
short name and share the same state if arguments "name" and "variable" are
not specified. Now they are globally unique.
* Move Lib/tkinter/test/test_tkinter/ to Lib/test/test_tkinter/.
* Move Lib/tkinter/test/test_ttk/ to Lib/test/test_ttk/.
* Add Lib/test/test_ttk/__init__.py based on test_ttk_guionly.py.
* Add Lib/test/test_tkinter/__init__.py
* Remove old Lib/test/test_tk.py.
* Remove old Lib/test/test_ttk_guionly.py.
* Add __main__ sub-modules.
* Update imports and update references to rename files.
Christopher Chavez
Alex Waygood
Serhiy Storchaka
Victor Stinner