Qt6 Migration: BUILD_RTI guards und CMake fixes

- BUILD_RTI conditional compilation für RTI Connext DDS dependencies
- Namespace fixes in core_dtc.h (Core:: → DDS::Core::)
- CMakeLists.txt: BUILD_RTI option und conditional dependencies
- Handler minelayer: namespace closing mit BUILD_RTI guard
- Build erfolgreich mit BUILD_RTI=OFF validiert

Signed-off-by: Torsten Wierschin <torsten.wierschin@life-maps.com>

qt6-after/qt6-migrated-legatus/Lts/Common/PluginInterfaces/data_plugin_interface.h

@@ -26,8 +26,10 @@ class Interface
     virtual ~Interface() = default;
 };
 
-class Plugin
+class Plugin : public QObject
 {
+  Q_OBJECT
+
   public:
     Plugin() = default;
     virtual ~Plugin() = default;