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/quick/QWidgetAdapter_quick.cpp

@@ -231,6 +231,11 @@ void QWidgetAdapter::releaseMouse()
     QQuickItem::ungrabMouse();
 }
 
+void QWidgetAdapter::releaseKeyboard()
+{
+    qWarning() << Q_FUNC_INFO << "Implement me";
+}
+
 void QWidgetAdapter::setMinimumSize(QSize sz)
 {
     if (minimumSize() != sz) {
@@ -554,6 +559,11 @@ void QWidgetAdapter::render(QPainter *)
     qWarning() << Q_FUNC_INFO << "Implement me";
 }
 
+void QWidgetAdapter::setMouseTracking(bool)
+{
+    qWarning() << Q_FUNC_INFO << "Implement me";
+}
+
 bool QWidgetAdapter::event(QEvent *ev)
 {
     if (ev->type() == QEvent::Close)