qtquick: Start using the WidgetResizeHandler

It's no longer commented out in FloatingWindow.
Doesn't do much for QtQuick, but at least we don't have different
code paths

Making it work is next.

src/private/WidgetResizeHandler.cpp

@@ -42,7 +42,7 @@ int widgetResizeHandlerMargin = 4; //4 pixel
 using namespace KDDockWidgets;
 
 bool WidgetResizeHandler::s_disableAllHandlers = false;
-WidgetResizeHandler::WidgetResizeHandler(QWidget *target)
+WidgetResizeHandler::WidgetResizeHandler(QWidgetOrQuick *target)
     : QObject(target)
 {
     setTarget(target);
@@ -317,7 +317,7 @@ bool WidgetResizeHandler::handleWindowsNativeEvent(FloatingWindow *w, const QByt
 
 #endif
 
-void WidgetResizeHandler::setTarget(QWidget *w)
+void WidgetResizeHandler::setTarget(QWidgetOrQuick *w)
 {
     if (w) {
         mTarget = w;