Add support for rmw zenoh to the RMW extension

[tfoote]

Following up availability announced here: https://discourse.ros.org/t/rmw-zenoh-binaries-for-rolling-jazzy-and-humble/41395

The necessary steps to demo are here.

FROM ros:rolling

RUN apt-get update \
    && apt-get install -qy ros-rolling-rmw-zenoh-cpp ros-rolling-demo-nodes-cpp


ENV RMW_IMPLEMENTATION=rmw_zenoh_cpp


## See the demo

#. /opt/ros/rolling/setup.bash
#ros2 run rmw_zenoh_cpp rmw_zenohd &
#ros2 run demo_nodes_cpp listener &
#ros2 run demo_nodes_cpp talker