Add rmw_get_gid_for_client method

[ihasdapie]

Add rmw_get_gid_for_client method. This is needed for the service introspection feature (https://github.com/ros2/ros2/issues/1285) to populate client uuid fields.

Link to impl PRs:

• https://github.com/ros2/rmw_fastrtps/pull/631
• https://github.com/ros2/rmw_cyclonedds/pull/402
• https://github.com/ros2/rmw_connextdds/pull/92
• https://github.com/ros2/rmw_implementation/pull/206

Signed-off-by: Brian Chen brian.chen@openrobotics.org

[jacobperron]

I don't think we need a rmw_get_gid_for_service for the service introspection feature, but I don't think it hurts to add such an API for symmetry. I can create a ticket for this.

[jacobperron]

Full CI for all connected PRs:

• Linux
• Linux-aarch64
• Windows

Connected PRs:

• https://github.com/ros2/rmw_fastrtps/pull/631
• https://github.com/ros2/rmw_cyclonedds/pull/402
• https://github.com/ros2/rmw_connextdds/pull/92
• https://github.com/ros2/rmw_implementation/pull/206