Use of rclcpp::Node is unsafe in an asynchronous setting and can cause segfaults and undefined behavior if such objects are constructed and/or destructed simultaneously.

See ros2/rosbag2#329 where this directly caused a reproducible crash. While the particular crash was averted in ros2/rosbag2#338, the constructor/destructor still use the unsafe functions rcl_node_init/rcl_node_fini.

Either these functions should be made threadsafe or they should be documented as unsafe and audited/instrumented to detect such unsafe usage.