Make code Qt6 ready

Test mode: for kdev-php, kdev-css & kdevelop's qmake support I generated the parser/ subdirectory twice with the branch, qt5 & qt6 builds, and once with current master. Looking at the diff of the generated files, the only difference seen was the QString::midRef generated code ported to use QStringView::mid instead and some order of code generated from hash map lists.

@kfunk @mwolff