[kstyle] Disable window move on Wayland

Unfortunately we cannot support moving windows from the style on Wayland
(yet). To move a window we need the (Xdg)ShellSurface and the wl_seat.
Through the integration plugin we can get the ShellSurface, but not the
seat. Thus we cannot invoke the feature through KWayland.

We either need to extend the native interface and/or extend QWindow to
expose a startSystemMove (QPlatformWindow already supports a
startSystemResize).

REVIEW: 127301

kstyle/breezewindowmanager.cpp

@@ -570,6 +570,12 @@ namespace Breeze
     bool WindowManager::canDrag( QWidget* widget, QWidget* child, const QPoint& position )
     {
 
+        // do not start drag on Wayland, this is not yet supported
+        // To implement integration with KWayland is required
+        // and QtWayland must support getting the wl_seat.
+        // Other option would be adding support to Qt for starting a move
+        if( Helper::isWayland() ) return false;
+
         // retrieve child at given position and check cursor again
         if( child && child->cursor().shape() != Qt::ArrowCursor ) return false;