Fix button to Qt::MouseButton mapping
Even though the names seem to match, QtWayland maps button values to enum values in ascendung order (as it does on X11). The wrong mapping is usually not a problem because we send the native button events to clients. However when the Qt names or values are used for communication between KWin and a client this leads to misunderstandings. BUG:465463 FIXED-IN:5.27.1