tests: add smoke-test executables for Lts/DDS placeholders during migration

Lts/DDS/DdsUnitTestsPlaceholder/ddsFunctionTopicTests_smoke.cpp

@@ -0,0 +1,5 @@
+#include <iostream>
+int main() {
+  std::cout << "[smoke] ddsFunctionTopicTests_smoke running" << std::endl;
+  return 0;
+}