Add lidar object segmentation op

[Qirui-jiao]

Built upon the mmdet3d Inferencer.

[gemini-code-assist]

Code Review

This pull request introduces a LiDARSegmentationMapper for segmenting LiDAR data, leveraging the mmdet3d library. The overall implementation is a good starting point, but there are several areas that require attention. I've identified a critical bug in error handling within prepare_mmlab_model, where an exception is not properly raised. Additionally, the same function introduces a heavy dependency by cloning an entire Git repository and contains hardcoded logic for model downloading, which impacts maintainability and portability. The new test file also has significant code duplication that could be refactored. I have provided specific comments and suggestions to address these issues.