QPainterStateGuard: make InitialState enum scoped

Address comment from header review,
amends 9ecf47a8a8d11227ecf192246d7df7c2c4dc9105.

Task-number: QTBUG-132090
Pick-to: 6.9
Change-Id: Idddca104b93ee23f4bac8621f1087a0ae7a1fe24
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

src/gui/painting/qpainterstateguard.cpp

@@ -30,10 +30,11 @@ QT_BEGIN_NAMESPACE
 */
 
 /*!
-    \fn QPainterStateGuard::QPainterStateGuard(QPainter *painter, InitialState state = Save)
+    \fn QPainterStateGuard::QPainterStateGuard(QPainter *painter, InitialState state = InitialState::Save)
     Constructs a QPainterStateGuard and calls save() on \a painter if \a state
-    is \c Save (which is the default). When QPainterStateGuard is destroyed, restore()
-    is called as often as save() was called to restore the QPainter's state.
+    is \c InitialState::Save (which is the default). When QPainterStateGuard is
+    destroyed, restore() is called as often as save() was called to restore the
+    QPainter's state.
 */
 
 /*!

src/gui/painting/qpainterstateguard.h

@@ -13,14 +13,13 @@ class QPainterStateGuard
 {
     Q_DISABLE_COPY_MOVE(QPainterStateGuard)
 public:
-    enum InitialState
-    {
+    enum class InitialState : quint8 {
         Save,
         NoSave,
     };
 
     Q_NODISCARD_CTOR
-    explicit QPainterStateGuard(QPainter *painter, InitialState state = Save)
+    explicit QPainterStateGuard(QPainter *painter, InitialState state = InitialState::Save)
         : m_painter(painter)
     {
         Q_ASSERT(painter);