Override QTabBar::tabInserted insted of QTabWidget::tabInserted

Since we're moving logic to tab bar instead of tab widget.
Otherwise calling count() on the tab bar while QTabWidget::tabInserted
is running can give the wrong value. So settle with a single class.

src/controllers/Stack.cpp

@@ -154,16 +154,6 @@ bool Stack::isMDI() const
     return m_group && m_group->isMDI();
 }
 
-void Stack::onTabInserted()
-{
-    m_group->onDockWidgetCountChanged();
-}
-
-void Stack::onTabRemoved()
-{
-    m_group->onDockWidgetCountChanged();
-}
-
 bool Stack::onMouseDoubleClick(QPoint localPos)
 {
     // User clicked the empty space of the tab widget and we don't have title bar

src/controllers/Stack.h

@@ -81,8 +81,6 @@ public:
     KDBindings::Signal<bool> tabBarAutoHideChanged;
 
 public: // TODOm3
-    void onTabInserted();
-    void onTabRemoved();
     bool onMouseDoubleClick(QPoint localPos);
 
 private:

src/qtwidgets/views/Stack_qtwidgets.cpp

@@ -97,16 +97,6 @@ void Stack_qtwidgets::mousePressEvent(QMouseEvent *ev)
     }
 }
 
-void Stack_qtwidgets::tabInserted(int)
-{
-    m_stack->onTabInserted();
-}
-
-void Stack_qtwidgets::tabRemoved(int)
-{
-    m_stack->onTabRemoved();
-}
-
 void Stack_qtwidgets::setupTabBarButtons()
 {
     if (!(Config::self().flags() & Config::Flag_ShowButtonsOnTabBarIfTitleBarHidden))

src/qtwidgets/views/Stack_qtwidgets.h

@@ -47,8 +47,6 @@ public:
 public: // TODOm3: make protected
     void mouseDoubleClickEvent(QMouseEvent *) override;
     void mousePressEvent(QMouseEvent *) override;
-    void tabInserted(int index) override;
-    void tabRemoved(int index) override;
 
     /// @brief Shows the context menu. Override to implement your own context menu.
     /// By default it's used to honour Config::Flag_AllowSwitchingTabsViaMenu

src/qtwidgets/views/TabBar_qtwidgets.cpp

@@ -139,12 +139,14 @@ void TabBar_qtwidgets::tabInserted(int index)
 {
     QTabBar::tabInserted(index);
     Q_EMIT dockWidgetInserted(index);
+    m_tabBar->group()->onDockWidgetCountChanged();
 }
 
 void TabBar_qtwidgets::tabRemoved(int index)
 {
     QTabBar::tabRemoved(index);
     Q_EMIT dockWidgetRemoved(index);
+    m_tabBar->group()->onDockWidgetCountChanged();
 }
 
 void TabBar_qtwidgets::setCurrentIndex(int index)