Run test_tracetools tests against rmw_zenoh_cpp

[christophebedard]

Requires ros2/rmw_zenoh#294

This is a draft, because it requires having the Zenoh router running:

$ ros2 run rmw_zenoh_cpp rmw_zenohd

Also, this probably should not be merged before rmw_zenoh_cpp officially becomes a tier 1 rmw implementation and gets included in the ROS 2 core (and ros2.repos), although the rmw_zenoh_cpp will just be skipped if it's not found.

[fujitatomoya]

This is a draft, because it requires having the Zenoh router running

CI is gonna be responsible for this, right? unless, rmw_zenoh_cpp cannot run the CI or any tests? I do not really know what the plan here though...

[clalancette]

CI is gonna be responsible for this, right? unless, rmw_zenoh_cpp cannot run the CI or any tests? I do not really know what the plan here though...

Yeah, we are going to have to figure out how to ensure that the router is running (both for ci.ros2.org and the Rpr jobs) so that the rmw_zenoh_cpp tests can run and pass.

[christophebedard]

In this case, I can easily launch zenohd before launching the nodes that get traced (e.g., in tracetools_test's TraceTestCase), but yeah we need a universal solution.