Co-authored-by: Michael Goderbauer <goderbauer@google.com>

* Replace references to LinearProgressIndicator in CircularProgressIndicator example

* Add test

* fix copyright header

When I added localizations for shortcut keys, I added some that actually can't be shortcut keys, so I'm removing them again. These are mostly Japanese-specific keys that don't even appear on modern keyboards for the most part.

Also, added menuBarMenuLabel for an accessibility label for menu bar menus.

I modified the code for the localization generation scripts to add a --remove-undefined flag that will remove any localizations that don't appear in the canonical locale.