ros2: add basic support for ROS 2 tracesThis adds the basic elements for a new ROS 2 plugin and defines thebasic layout for ROS 2 traces.Signed-off-by: Christophe Bedard <bedard.christophe@gmail.com>Change-Id: Ib59efa443a30951d4d9e4906858bcdc9ce25569cReviewed-on: https://git.eclipse.org/r/c/tracecompass.incubator/org.eclipse.tracecompass.incubator/+/192541Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>