GCodeTimeEstimator uses annotated gcode in place of processing m600 lines to detect color print changes.

WARNING -> After this commit the exported gcode will contain the extra lines used by the time estimator. They will be removed by a future commit when a new post-process method will be implemented.

src/libslic3r/GCode.cpp

@@ -1525,6 +1525,8 @@ void GCode::process_layer(
     {
         // add tag for analyzer
         gcode += "; " + GCodeAnalyzer::Color_Change_Tag + "\n";
+        // add tag for time estimator
+        gcode += "; " + GCodeTimeEstimator::Color_Change_Tag + "\n";
         gcode += "M600\n";
     }