Remove STUB files, use real dependencies

- Removed all STUB files for external dependencies:
  - lts_session_stub.h/cpp
  - lts_session_data_dds_stub.h/cpp
  - lts_session_lock_handler_stub.h
  - elevation_map_manager.h/cpp (entire ElevationMap STUB)
  - avm_enums_stub.hpp
  - Test files for STUBs

- Updated LtsSession/CMakeLists.txt:
  - Removed conditional BUILD_RTI logic for STUBs
  - Always use real implementation files
  - BUILD_RTI=ON is now the default

- External dependencies are now expected in ./external/
  - RTI Connext DDS 7.7.0
  - ArcGIS SDK (runtime mount)
  - Other deps to be integrated step by step

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

qt6-after/qt6-migrated-legatus/Lts/Viewer/SituationMap/ElevationMap/CMakeLists.txt

@@ -1,20 +0,0 @@
-#
-# ElevationMap STUB - Qt6 Migration
-# Minimal implementation to allow LtsElevation compilation
-#
-
-NGL_ADD_LIBRARY2(WS SV HLA situationMapElevationMap SHARED
-  elevation_map_manager.cpp
-  elevation_map_manager.h
-)
-
-NGL_TARGET_INCLUDE_DIRECTORIES(situationMapElevationMap
-  PUBLIC
-    ${CMAKE_CURRENT_SOURCE_DIR}/../../include/Viewer/SituationMap/ElevationMap
-)
-
-NGL_TARGET_LINK_LIBRARIES(situationMapElevationMap
-  PUBLIC
-    Qt6::Core
-    Qt6::Gui
-)