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/debugmessagesmodel.cpp

@@ -111,6 +111,7 @@ void DebugMessagesModel::finalize()
 {
     setCollapsedRowCount(Constants::QML_MIN_LEVEL + 1);
     setExpandedRowCount(m_maximumMsgType + 2);
+    QmlProfilerTimelineModel::finalize();
 }
 
 void DebugMessagesModel::clear()