Utils: Modernize further

Many issues, mostly in headers, were not addressed in
e38410b76c

modernize-use-auto
modernize-use-nullptr
modernize-use-override
modernize-use-using
modernize-use-default-member-init
modernize-use-equals-default

Change-Id: I320a51726db881e582b898948d53735ebb06887a
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/savedaction.cpp

@@ -56,7 +56,6 @@ namespace Utils {
 SavedAction::SavedAction(QObject *parent)
   : QAction(parent)
 {
-    m_widget = nullptr;
     connect(this, &QAction::triggered, this, &SavedAction::actionTriggered);
 }