Support training of Voxel Mamba on Waymo

[gwenzhang]

Motivation

Support Voxel Mamba (https://arxiv.org/abs/2406.10700) in Openpcdet.

Modification

Add file pcdet/models/backbones_3d/voxel_mamba.py, which includes the sparse backbone of Voxel Mamba. Add file pcdet/models/model_utils/voxel_mamba_utils.py, which includes the utility functions for Voxel Mamba. Add file tools/process_tools/create_hilbert_curve.py, which includes the template codes for Voxel Mamba. Change file pcdet/models/backbones_3d/__init__.py, which adds the Voxel Mamba in the init file.

Mamba

Download the mamba package from https://github.com/gwenzhang/Voxel-Mamba/tree/master/mamba or google drive (https://drive.google.com/file/d/12BfIyvsA_BiX3IzgTEFfhd6RCEigQPvW/view?usp=drive_link) and pip install -e . in local file for the reason (https://github.com/open-mmlab/OpenPCDet/issues/960).