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/LtsDataView/tree_view.h

@@ -0,0 +1,37 @@
+/**
+ * @RDE_HEADER@
+ * A QTreeView with some events catched
+ * $Id$
+ * $HeadURL$
+ * $Author$
+ *
+ * Created by Mike Wille, SLSE, 2016-10-07
+ */
+
+#pragma once
+
+#include <QTreeView>
+
+
+namespace LtsDataView
+{
+class TreeView final : public QTreeView
+{
+  Q_OBJECT
+
+public:
+  using QTreeView::QTreeView;
+
+  void dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight,
+                   const QVector<int> &roles) override;
+protected:
+  void keyPressEvent(QKeyEvent *event) override;
+  bool edit(const QModelIndex &index, EditTrigger trigger, QEvent *event) override;
+  bool viewportEvent(QEvent *event) override;
+
+signals:
+  void signalCopyToClipBoard();
+private:
+  QPoint m_toolTipPos;
+};
+} // namespace LtsDataView