Qt6 Migration: BUILD_RTI guards und CMake fixes

- BUILD_RTI conditional compilation für RTI Connext DDS dependencies
- Namespace fixes in core_dtc.h (Core:: → DDS::Core::)
- CMakeLists.txt: BUILD_RTI option und conditional dependencies
- Handler minelayer: namespace closing mit BUILD_RTI guard
- Build erfolgreich mit BUILD_RTI=OFF validiert

Signed-off-by: Torsten Wierschin <torsten.wierschin@life-maps.com>

qt6-after/qt6-migrated-legatus/tests/test_json_keys.h.cpp

@@ -1,16 +1,16 @@
 #include <gtest/gtest.h>
 
-TEST(json_keys.hTest, CompilationStub)
+TEST(json_keys_headerTest, CompilationStub)
 {
     EXPECT_TRUE(true);
 }
 
-TEST(json_keys.hTest, Qt6ApiCompatibility)
+TEST(json_keys_headerTest, Qt6ApiCompatibility)
 {
     EXPECT_TRUE(true);
 }
 
-TEST(json_keys.hTest, BasicFunctionality)
+TEST(json_keys_headerTest, BasicFunctionality)
 {
     EXPECT_TRUE(true);
 }