Utils: Add an AspectContainer::changed() signal

In contrast to applied() only emitted if anything was dirty before.

Ideally, applied() would not be needed, but I am not sure about
downstream uses.

Change-Id: Ie0c293b8730c503fc4409884a33207ee9ca5f129
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/utils/aspects.cpp

@@ -2475,10 +2475,15 @@ void AspectContainer::setSettingsGroups(const QString &groupKey, const QString &
 
 void AspectContainer::apply()
 {
+    const bool willChange = isDirty();
+
     for (BaseAspect *aspect : std::as_const(d->m_items))
         aspect->apply();
 
     emit applied();
+
+    if (willChange)
+        emit changed();
 }
 
 void AspectContainer::cancel()

src/libs/utils/aspects.h

@@ -695,6 +695,7 @@ public:
 
 signals:
     void applied();
+    void changed();
     void fromMapFinished();
 
 private: