This required adding a new method symXModXToKeyQt since
symXToKeyQt (without modifier as input) has no way to find out
whether to use XK_KP_1 or XK_1. For this reason symXToKeyQt is now
deprecated.
Includes a unittest for keyQtToSymX, keyQtToModX and symXModXToKeyQt.
CCBUG: 183458