QmlProfiler: Move parts of model manager and trace file to Timeline

This way we can use the trace file loading and saving mechanism for
other profilers.

Change-Id: I98ec1cdde6f7abcea152cabf72e64d4e696dfa59
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/qmlprofiler/qmlprofilernotesmodel.h

@@ -42,6 +42,7 @@ public:
 
     const QVector<QmlNote> &notes() const;
     void setNotes(const QVector<QmlNote> &notes);
+    void addNote(const QmlNote &note);
     void clear() override;
 
 protected: