Registration of toolbar factory functions...

... reduces direct dependencies of ToolManager.cpp.

This frees four files from cycles:
DeviceToolBar
EditToolBar
MeterToolBar
MixerToolBar

Leaving 66 files still in the big s.c.c.

src/toolbars/ControlToolBar.cpp

@@ -1572,3 +1572,7 @@ TransportTracks GetAllPlaybackTracks(TrackList &trackList, bool selectedOnly, bo
 #endif
    return result;
 }
+
+static RegisteredToolbarFactory factory{ TransportBarID,
+   [](AudacityProject*){ return ToolBar::Holder{ safenew ControlToolBar }; }
+};