Add QT_NO_USHORT_STRINGS and make all of Qt build with it set.

ushort is what old pre-C++11 code used when it needed a primitive type instead of QChar. Since C++11, we have the superior char16_t, clearly a character type and not (also) an integer, so the vast majority of code has been ported already. Yet, QStringView (and, by extension, QAnyStringView) still accept ushort* as strings. Add an opt-out macro and make sure Qt compiles with it.