[Feature] Support training of BEVFusion

[JingweiZhang12]

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Motivation

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Modification

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BC-breaking (Optional)

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Use cases (Optional)

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Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
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: 65.00% and project coverage change: +0.01 🎉

Comparison is base (fa724b1) 46.90% compared to head (a2328ee) 46.91%.

❗ Current head a2328ee differs from pull request most recent head e127201. Consider uploading reports for the commit e127201 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #2558      +/-   ##
===========================================
+ Coverage    46.90%   46.91%   +0.01%     
===========================================
  Files          277      277              
  Lines        23378    23381       +3     
  Branches      3644     3644              
===========================================
+ Hits         10965    10969       +4     
+ Misses       11721    11719       -2     
- Partials       692      693       +1     

Flag	Coverage Δ
unittests	46.91% <65.00%> (+0.01%)	⬆️

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Impacted Files	Coverage Δ
mmdet3d/models/data_preprocessors/utils.py	22.72% <50.00%> (+3.67%)	⬆️
mmdet3d/engine/hooks/disable_object_sample_hook.py	84.37% <60.00%> (-4.92%)	⬇️
...t3d/models/data_preprocessors/data_preprocessor.py	31.91% <72.72%> (+0.69%)	⬆️

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