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_p.h

@@ -12,7 +12,8 @@
 #ifndef KD_WIDGET_RESIZE_HANDLER_P_H
 #define KD_WIDGET_RESIZE_HANDLER_P_H
 
-#include <QWidget>
+#include "QWidgetAdapter.h"
+
 #include <QPoint>
 #include <QDebug>
 
@@ -28,10 +29,10 @@ class WidgetResizeHandler : public QObject
 {
     Q_OBJECT
 public:
-    explicit WidgetResizeHandler(QWidget *target = nullptr);
+    explicit WidgetResizeHandler(QWidgetOrQuick *target = nullptr);
     ~WidgetResizeHandler() override;
 
-    void setTarget(QWidget *w);
+    void setTarget(QWidgetOrQuick *w);
 
 #ifdef Q_OS_WIN
     static bool handleWindowsNativeEvent(FloatingWindow *w, const QByteArray &eventType, void *message, long *result);
@@ -55,7 +56,7 @@ private:
     void mouseMoveEvent(QMouseEvent *e);
     void updateCursor(CursorPosition m);
     CursorPosition cursorPosition(QPoint) const;
-    QWidget *mTarget = nullptr;
+    QWidgetOrQuick *mTarget = nullptr;
     CursorPosition mCursorPos = CursorPosition::Undefined;
     QPoint mNewPosition;
     bool mResizeWidget = false;