Add missing qquaternion.h includes

The qquaternion.h include will vanish from qmatrix4x4.h soon, but some
TUs depended on on the transitive include.

This patch includes qquaternion.h into all TUs that use QQuaternion,
but didn't include its header.

I didn't check all the individual TU's history to make a detailed
"amends", so I'll just pick this all the way back, knowing there may
have been more users in older branches, or some TUs don't exist there,
but it since we're not picking the removal of qquaternion.h from
qmatrix4x4.h further than 6.10, I don't need to do detailed
checking. CI will tell me when something's wrong.

Pick-to: 6.8 6.5
Change-Id: Icf0db8ba4f12421fd46f9d1041f235bf4cc2c12b
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit bd1fa8379c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit bde0dd48e2)

examples/widgets/rhi/cuberhiwidget/examplewidget.cpp

@@ -3,8 +3,10 @@
 
 #include "examplewidget.h"
 #include "cube.h"
+
 #include <QFile>
 #include <QPainter>
+#include <QtGui/qquaternion.h>
 
 static const QSize CUBE_TEX_SIZE(512, 512);
 

tests/auto/gui/math3d/qmatrixnxn/tst_qmatrixnxn.cpp

@@ -3,7 +3,9 @@
 
 #include <QTest>
 #include <QtCore/qmath.h>
+
 #include <QtGui/qmatrix4x4.h>
+#include <QtGui/qquaternion.h>
 
 class tst_QMatrixNxN : public QObject
 {

tests/manual/rhi/rhiwidgetproto/examplewidget.cpp

@@ -3,8 +3,11 @@
 
 #include "examplewidget.h"
 #include "../shared/cube.h"
+
 #include <QFile>
+
 #include <QPainter>
+#include <QtGui/qquaternion.h>
 
 static const QSize CUBE_TEX_SIZE(512, 512);
 

tests/manual/stereographicsview/mygraphicsview.cpp

@@ -2,9 +2,12 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
 
 #include "mygraphicsview.h"
+
 #include <QResizeEvent>
 #include <QFileDialog>
 
+#include <QtGui/qquaternion.h>
+
 Q_OPENGL_EXPORT QImage qt_gl_read_framebuffer(const QSize &size, bool alpha_format, bool include_alpha);
 
 MyGraphicsView::MyGraphicsView(QWidget *parent) :