Update SignalHandler get_global_signal_handler to avoid complex types…

… in static memory (#2316)

* Update SignalHandler get_global_signal_handler to avoid complex types in static memory

This was flagged by msan as a problem.

There's a description of why this is a potential problem here: https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables

Signed-off-by: Tully Foote <tullyfoote@intrinsic.ai>
Co-authored-by: William Woodall <william+github@osrfoundation.org>

rclcpp/src/rclcpp/signal_handler.cpp

@@ -113,7 +113,7 @@ SignalHandler::get_logger()
 SignalHandler &
 SignalHandler::get_global_signal_handler()
 {
-  static SignalHandler signal_handler;
+  static SignalHandler & signal_handler = *new SignalHandler();
   return signal_handler;
 }