[Enhance] Support more tensor-like operations for data structures.

[Xiangxu-0103]

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Motivation

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Modification

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BC-breaking (Optional)

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Checklist

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2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Patch coverage: 43.33% and no project coverage change.

Comparison is base (864ed34) 47.12% compared to head (15a6c25) 47.13%.

❗ Current head 15a6c25 differs from pull request most recent head e40452b. Consider uploading reports for the commit e40452b to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           dev-1.x    #2501   +/-   ##
========================================
  Coverage    47.12%   47.13%           
========================================
  Files          276      276           
  Lines        23011    23037   +26     
  Branches      3582     3582           
========================================
+ Hits         10845    10858   +13     
- Misses       11484    11497   +13     
  Partials       682      682           

Flag	Coverage Δ
unittests	47.13% <43.33%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
mmdet3d/datasets/convert_utils.py	0.00% <ø> (ø)
mmdet3d/datasets/transforms/loading.py	44.91% <0.00%> (ø)
mmdet3d/datasets/transforms/transforms_3d.py	40.09% <0.00%> (ø)
mmdet3d/evaluation/metrics/kitti_metric.py	9.09% <ø> (ø)
mmdet3d/evaluation/metrics/waymo_metric.py	8.11% <ø> (ø)
mmdet3d/structures/points/base_points.py	83.33% <45.45%> (-2.23%)	⬇️
mmdet3d/structures/bbox_3d/base_box3d.py	83.11% <53.33%> (-2.13%)	⬇️

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