BUILD_RTI conditional fixes and Qt6 API updates

- cmake/FindRTI.cmake: Add INTERFACE placeholder targets when RTI not found
- cmake/FindRTI.cmake: Force BUILD_RTI=OFF when RTI not installed
- Lts/Common/LtsSession/CMakeLists.txt: Make LtsSessionDataDds conditional on BUILD_RTI
- Lts/Viewer/CMakeLists.txt: Make LtsDataView conditional on BUILD_RTI
- Lts/Plugins/*/CMakeLists.txt: 97 plugin files wrapped in BUILD_RTI conditionals
- cmake/NGLMacros.cmake: Fix NGL_ADD_BIG_RESOURCES macro (removed premature return())
- Multiple Qt6 API fixes: QLinkedList→std::list, QStringRef→QStringView, etc.
- BUILD_RTI_FIXES_SUMMARY.md: Comprehensive documentation of all fixes

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

qt6-after/qt6-migrated-legatus/Lts/DDS/DdsUnitTests/function_topic_tests.cpp

@@ -2,7 +2,7 @@
 
 
 #include "function_topic_tests.h"
-#include <Common/ProjectConfig/project_defines.h>
+#include <Lts/Common/ProjectConfig/project_defines.h>
 #include <DDS/DDSConnector/subscriber.h>
 #include <DDS/DDSConnector/publisher.h>
 
@@ -29,7 +29,7 @@ int main(int argc, char *argv[])
 
 FunctionTopicTests::FunctionTopicTests()
   : m_mainThreadId(QThread::currentThreadId())
-  , m_logger(NGL::NGLLoggerBootstrap::getNGLRootLogger().getNGLLogger("UnitTests.FunctionTopicTests"))
+  .getNGLLogger("UnitTests.FunctionTopicTests"))
 {
   qRegisterMetaType<DdsUnitTests::FunctionReply>("DdsUnitTests::FunctionReply");
   qRegisterMetaType<DdsUnitTests::FunctionReplyWithState>("DdsUnitTests::FunctionReplyWithState");