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/Viewer/SituationMap/Common/exception.h

@@ -0,0 +1,93 @@
+/**
+**
+** @RDE_HEADER@
+** Implementation of Splines
+** $Id$
+** $HeadURL$
+** $Author$
+** -----------------------------------------------------------------------------------------------
+**
+** Hardware-Environment: Intel-PC
+** Software-Environment: Windows 7, Qt 5.4. ArcGIS 10.2.5
+**
+** Language ........: C++ 11
+**
+** -----------------------------------------------------------------------------------------------
+**
+** Author ...........: Joerg Turla, SPD G, Tel. 3132
+**
+** -----------------------------------------------------------------------------------------------
+**
+** Notes .........:
+**
+**   19.06.2012, JT  : Urversion for use in VIntel project
+**   12.08.2015, JT  : adapted to SituationMap
+**
+** -----------------------------------------------------------------------------------------------
+*/
+
+#pragma once
+
+
+#include <QtCore/QString>
+
+namespace SituationMap
+{
+/**
+   \class   Exception exception.h
+   \brief   Basisklasse for Exception-Handling
+
+   The class Exception defines a very simple exception handler, that will be able to return
+   a string message when an exception is thrown
+*/
+
+class Exception
+{
+public:
+
+  Exception()
+    : _message(QLatin1String("Error"))
+  {}
+
+  Exception(const Exception &) = default;
+
+  explicit Exception(const QString    &msg)
+    : _message(msg)
+  {}
+
+
+  // explicit is not used here because
+  // throw SituationMap::Exception(__FILE__, __LINE__, "Message" );
+  // will become more complicated
+
+  Exception(const char *Source
+            , unsigned int lineNo
+            , const char *msg)
+    : Exception(QLatin1String(Source), lineNo, QLatin1String(msg))
+  {}
+
+  Exception(const char *Source
+            , unsigned int lineNo
+            , const QString &msg)
+    : Exception(QLatin1String(Source), lineNo, msg)
+  {}
+
+  Exception(const QString &Source
+            , unsigned int lineNo
+            , const QString &msg)
+    : _message(QStringLiteral("\"%1\" in %2 at %3").arg(msg, Source).arg(lineNo))
+  {}
+
+  ~Exception() = default;
+  Exception &operator = (const Exception &e) = default;
+
+
+  QString getMessage() const { return _message; } //!< returns a specific error message as QString
+
+protected:
+
+  QString _message;
+
+};
+
+} // namespace SituationMap