Replace static_casts by QOverload where possible

Mainly to get rid of the QProcess::finished deprecation warning.

Also adjust coding style in the surrounding connects when needed.

Change-Id: I12f9b248c7974b892c4a069356e578e80f8c59e9
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/coreplugin/sidebarwidget.cpp

@@ -99,7 +99,7 @@ SideBarWidget::SideBarWidget(SideBar *sideBar, const QString &id)
     }
     setCurrentItem(t);
 
-    connect(m_comboBox, static_cast<void (QComboBox::*)(int)>(&QComboBox::currentIndexChanged),
+    connect(m_comboBox, QOverload<int>::of(&QComboBox::currentIndexChanged),
             this, &SideBarWidget::setCurrentIndex);
 }