[Feature] Support PGD and multi-view FCOS3D++ on Waymo

[sunjiahao1999]

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Motivation

Please describe the motivation of this PR and the goal you want to achieve through this PR.

Modification

Support PGD front-of-view / multi-view on Waymo
Support multi-view FCOS3D++ on Waymo
Update Waymo-mini and waymo_infos_xxx.pkl link and related docs

BC-breaking (Optional)

Does the modification introduce changes that break the back-compatibility of the downstream repos?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

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.

[CLAassistant]

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2 out of 3 committers have signed the CLA.

✅ JingweiZhang12
✅ sunjiahao1999
❌ sjh

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[codecov]

Codecov Report

Attention: 23 lines in your changes are missing coverage. Please review.

Comparison is base (762e3b5) 47.24% compared to head (be43c4d) 47.26%.
Report is 2 commits behind head on dev-1.x.

Files	Patch %	Lines
mmdet3d/models/detectors/multiview_dfm.py	29.03%	22 Missing ⚠️
mmdet3d/models/detectors/dfm.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #2835      +/-   ##
===========================================
+ Coverage    47.24%   47.26%   +0.01%     
===========================================
  Files          277      277              
  Lines        23416    23415       -1     
  Branches      3657     3655       -2     
===========================================
+ Hits         11063    11067       +4     
+ Misses       11640    11635       -5     
  Partials       713      713              

Flag	Coverage Δ
unittests	47.26% <28.12%> (+0.01%)	⬆️

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