Complete Qt6 migration: full clean build green across groups G1-G12 incl. runtime plugin set

new_docker_build.sh gains Group 12 (212 GUI/Data plugins); fixes LtsUtilsGuiDds visibility (LTO-stripped exports), LtsProjectionWorkstation unity name shadow, 6 unity-off dirs (dup file-scope statics, ddsftc INTERFACE sources) and reconfigures BUILD_FILTERMANAGEMENT/BUILD_PLUGINS_SERVICEMONITOR=ON

qt6-after/qt6-migrated-legatus/Lts/Proxies/TrainingAreaBase/main_handler.cpp

@@ -207,7 +207,7 @@ ProjectDataManagement::RadioGroup MainHandler::exerciseRadioGroup() const
   }
 
   const auto ex = m_exmHandler->exercise(exerciseId());
-  if (ex.radioGroupId.is_set())
+  if (ex.radioGroupId.has_value())
     return m_pdmHandler->radioGroup(ex.radioGroupId.get());
   return ProjectDataManagement::RadioGroup();
 }