Revamp Queued Custom Type Ex: Fix includes

Fix includes order and add the needed ones to avoid transitive includes.

Remove QT_{BEGIN,END}_NAMESPACE because these are private Qt macros that
should not be used in the examples.

Task-number: QTBUG-117147
Pick-to: 6.6 6.5
Change-Id: I6caa0a59f2ab4dfec6fb558a0896c27b05b6a5db
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

examples/corelib/threads/queuedcustomtype/main.cpp

@@ -1,12 +1,17 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-#include <QApplication>
-#include <QPainter>
-#include <QTime>
 #include "block.h"
 #include "window.h"
 
+#include <QApplication>
+#include <QBrush>
+#include <QImage>
+#include <QPainter>
+#include <QPen>
+#include <QPointF>
+#include <QRect>
+
 QImage createImage(int width, int height)
 {
     QImage image(width, height, QImage::Format_RGB16);

examples/corelib/threads/queuedcustomtype/renderthread.cpp

@@ -1,9 +1,11 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
+#include "block.h"
 #include "renderthread.h"
 
 #include <QRandomGenerator>
+#include <QRgb>
 
 RenderThread::RenderThread(QObject *parent)
     : QThread(parent)

examples/corelib/threads/queuedcustomtype/renderthread.h

@@ -7,7 +7,8 @@
 #include <QImage>
 #include <QMutex>
 #include <QThread>
-#include "block.h"
+
+class Block;
 
 //! [RenderThread class definition]
 class RenderThread : public QThread

examples/corelib/threads/queuedcustomtype/window.cpp

@@ -1,8 +1,17 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
+#include "block.h"
+#include "renderthread.h"
 #include "window.h"
-#include <QtWidgets>
+
+#include <QFileDialog>
+#include <QGuiApplication>
+#include <QHBoxLayout>
+#include <QImageReader>
+#include <QPainter>
+#include <QScreen>
+#include <QVBoxLayout>
 
 //! [Window constructor start]
 Window::Window(QWidget *parent)

examples/corelib/threads/queuedcustomtype/window.h

@@ -4,13 +4,14 @@
 #ifndef WINDOW_H
 #define WINDOW_H
 
+#include <QImage>
+#include <QLabel>
+#include <QPixmap>
+#include <QPushButton>
 #include <QWidget>
-#include "renderthread.h"
 
-QT_BEGIN_NAMESPACE
-class QLabel;
-class QPushButton;
-QT_END_NAMESPACE
+class Block;
+class RenderThread;
 
 //! [Window class definition]
 class Window : public QWidget