cameras: fix topic namespaces

[dakejahl]

Problem
User reported issue in multi-vehicle sim where all camera topics end up with the same name /camera

After this PR
Topics are namespaced properly

/world/default/model/x500_mono_cam_down_1/model/mono_cam/link/camera_link/sensor/imager/camera_info
/world/default/model/x500_mono_cam_down_1/model/mono_cam/link/camera_link/sensor/imager/image
/world/default/model/x500_mono_cam_down_2/model/mono_cam/link/camera_link/sensor/imager/camera_info
/world/default/model/x500_mono_cam_down_2/model/mono_cam/link/camera_link/sensor/imager/image

[th-grimaldi]

I'm the user in question. This change works. It would be helpful to extend this change to other cameras and drones as well, instead of only mono_cam and the x500_mono_cam_down sdfs.

[dakejahl]

I'm the user in question. This change works. It would be helpful to extend this change to other cameras and drones as well, instead of only mono_cam and the x500_mono_cam_down sdfs.

@th-grimaldi all camera models have been updated. Let me know if this works.

[beniaminopozzan]

Thanks @dakejahl !
Tested on gz_x500_mono_cam, gz_x500_mono_cam_down and gz_x500_depth