Add BUILD_RTI guards to InfrastructureManagement and AudioVideoManagement DDS handlers

- ism_dtc_impl_custom.h/cpp: Wrap all DDS-dependent method declarations and implementations with BUILD_RTI guards
- dds_handler.cpp (InfrastructureManagement): Guard RTI DDS initialization code
- dds_handler.h/cpp (AudioVideoManagement): Guard DomainParticipant types and methods
- Enables building without RTI Connext DDS dependencies (BUILD_RTI=OFF)
- Stub types used when guards are disabled

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/Lts/Services/InfrastructureManagement/dds_handler.cpp

@@ -9,7 +9,9 @@
 
 #include "dds_handler.h"
 
+#if BUILD_RTI
 #include <DDS/Core/pacemaker.h>
+#endif
 
 namespace InfrastructureManagement
 {
@@ -28,6 +30,7 @@ bool DdsHandler::init(const QStringList &qosFileList)
     return false;
   }
 
+#if BUILD_RTI
   // default initialize Publisher and Subscriber
   m_ddsConnector->initPublisherSubscriber();
 
@@ -57,6 +60,9 @@ bool DdsHandler::init(const QStringList &qosFileList)
   }
 
   return bRet;
+#else
+  return true;
+#endif
 }
 
 } // Namespace PDM