Fix lidar visualization when gz_frame_id is specified

[iche033]

🦟 Bug fix

Summary

The lidar visualization plugin has an assumption that the frame_id in the lidar scan msg is the name of the lidar sensor and uses this to find the lidar entity in the ECM. With the changes in gazebosim/gz-sensors#447, this is no longer true. The lidar scan msg's frame_id is now correctly set to <gz_frame_id> or the sensor name if gz_frame_id is not supplied. This PR fixes lidar visualization by finding the lidar entity based on the subscribed topic name.

manually tested using gpu_lidar_sensor.sdf by adding <gz_frame_id> to the lidar sensor and verifying lidar visualization still works:

gpu_lidar_sensor.patch

diff --git a/examples/worlds/gpu_lidar_sensor.sdf b/examples/worlds/gpu_lidar_sensor.sdf
index 756de3eb3..8a7781f8c 100644
--- a/examples/worlds/gpu_lidar_sensor.sdf
+++ b/examples/worlds/gpu_lidar_sensor.sdf
@@ -139,6 +139,7 @@
         </visual>
 
         <sensor name='gpu_lidar' type='gpu_lidar'>
+          <gz_frame_id>my_lidar_frame_id</gz_frame_id>
           <topic>lidar</topic>
           <update_rate>10</update_rate>
           <lidar>

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
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• All tests passed (See test coverage)
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[caguero]

Should we do something to avoid this message to show up over and over if we don't find the entity?

[iche033]

Updated to print only once. I also added extra checks for null entity in case the lidar is deleted. cf6ed2c