Use versionless QtQuick imports
It ensures that we pull the latest features introduced in QtQuick in Qt6. This is the culprit of https://bugreports.qt.io/browse/QTBUG-111373 too.
org.kde.kirigami imports have not been adjusted because otherwise QML fails to recognize Kirigami. It's most likely connected to the fact that Kirigami installs its stuff in ${KDE_INSTALL_QMLDIR}/org/kde/kirigami.2 rather than ${KDE_INSTALL_QMLDIR}/org/kde/kirigami