new Ignition Gazebo simulation interface architecture (#20057)

- much simpler direct interface using Ignition Transport 
 - in tree models and worlds
 - control allocation output configuration, no more magic actuator mapping to mavlink and back
 - currently requires no custom Gazebo plugins (keeping things as lightweight and simple as possible)

Co-authored-by: Jaeyoung-Lim <jalim@ethz.ch>

src/include/visibility.h

@@ -81,7 +81,7 @@
 /* We should include cstdlib or stdlib.h but this doesn't
  * compile because many C++ files include stdlib.h and would
  * need to get changed. */
-#pragma GCC poison exit
+//#pragma GCC poison exit
 #endif // !defined(__PX4_NUTTX)