Interface to get pointcloud from SDF

[MA-Wenhui]

Desired behavior

Need an interface to get the world's all collisions and generate the 3d map(pointcloud).

Alternatives considered

I tried to parse sdf file to extract dae/stl/geometry, but it was too complicated since the sdf structures vary.

Implementation suggestion

There is a RayQuery based solution for gazebo-classic:

https://github.com/[arshadlab/gazebo_map_creator](https://github.com/arshadlab/gazebo_map_creator)

I didn't find the equivalent class for this usage in gz harmonic.

Additional context