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/Plugins/Messaging/Data/msg_data_plugin.h

@@ -13,10 +13,9 @@
 namespace Messaging
 {
 
-class DataPlugin final : public QObject, public DataPluginBase::Plugin
+class DataPlugin final : public DataPluginBase::Plugin
 {
   Q_PLUGIN_METADATA(IID "data:3:msg")
-  Q_INTERFACES(DataPluginBase::Plugin)
 
   Q_OBJECT
 public: