[mleitenstern]

Summary

Adds support for arbitrary extra per point fields (e.g. red, green, blue) that are passed through the whole pipeline into the final map, like intensity. Values keep their native datatype.

Companion PR in glim_ros2: 77

Changes

• New parameter sensors/extra_point_fields in config_sensors.json (default []).
• Fields are stored as gtsam_points aux attributes, so they survive sampling, filtering, submap merging and map saving.
• Field types are detected from the first message and recorded in meta/point_attribute_types of the dumped config.
• frame_to_pointcloud2 and the offline viewer PLY export write the fields with their native type.

Limitations

• Field names must not contain _ (not restored by PointCloudCPU::load).
• Requires use_random_grid_downsampling: true, since voxel grid sampling drops aux attributes.

Testing

• Builds on ROS 2 Jazzy with CUDA and viewer.
• Standalone test of the attributes through preprocessing, sampling, merging, save / load and ROS conversion.
• Mapping run on a recorded dataset.