Drip-feed FollowJointTrajectory goals to MotoROS2 one JointTrajectoryPoint at a time.
This is essentially a Python implementation of the FollowJointTrajectory action server in industrial_robot_client / motoman_driver.
WIP.
The node currently suffers a cpu leak, in the sense that consecutive goals cause the node to consume increasingly large amounts of CPU time, until a full core is consumed.