Don't use RTPS Participant name as node name

[ivanpauno]

This is what I mentioned here: ros2/ros2cli#464 (comment).

Currently, the node name and namespace are communicated making use of userData qos.
In case that that qos setting can be parsed in the way ros2 is using it, we're using the RTPS Participant name as a node name, and listing it.

The question is: is that exactly what we want?
I see some value of showing the user other Participants that weren't craeted with ROS, but probably, their name should be showed with a different prefix. An opt-in/opt-out flag to show them or not would also be nice.

In ros2/rmw_fastrtps#312, userData is now being use to communicate the Context name. Connext was failing to parse it, and then showing the RTPS Participant name.

We can take the following paths:

• Just show Participants that their userData can be parsed correctly (proposed in this PR).
• Don't change anything here, and accept the participant name to be showed as a node name. Make sure that the tests don't run nodes from a different implementation when they shouldn't (see Avoid using ros_testing, and use launch_testing instead ros2cli#464).

I don't know what's the best option, @hidmic @wjwwood opinions?

[hidmic]

I think this makes sense. If participants aren't nodes, what are they in this context? There's no concept of a participant in ROS, so nothing should be shown. You can always use DDS tools to introspect your system if need be.

[wjwwood]

I guess it makes sense too, based on @hidmic's reasoning.

[ivanpauno]

• Linux
• macOS
• Windows

[ivanpauno]

Failures are unrelated, merging!