TrackVertexMonitor initialises the tool TrackVertexer not at start but later

The TrackVertexMonitor was recently put into Hlt2B2CC_BsToJpsiPhi and thus uses the TrackVertexer ToolHandle when running HLT2. It was observed that the tool initialisation only happens after a long time after starting to process events. This suggests that the tool is at most only initialised when the trigger line fires; this delayed initialisation will avoid the tool config to be captured by the TCK and should thus be avoided.

Screenshot of the observation is Attachment 4 in https://lblogbook.cern.ch/HLT/729

This can probably be solved either by providing the TrackVertexer as public tool centrally, or using a different constructor for the ToolHandle, i.e.

-ToolHandle<ITrackVertexer> m_vertexer{"TrackVertexer"};
+ToolHandle<ITrackVertexer> m_vertexer{this, "TrackVertexer", "TrackVertexer"};

/cc @rmatev