[Enhance] Benchmark PAConv on S3DIS dataset

[Wuziyi616]

Release PAConv model on S3DIS semantic segmentation task.

Just FYI, the paper's result is 66.33% while ours is 66.65%.

[Wuziyi616]

@ZwwWayne checkpoint and log need to be uploaded

[codecov]

Codecov Report

Merging #809 (7cecec4) into master (43b4632) will increase coverage by 0.12%.
The diff coverage is 100.00%.

❗ Current head 7cecec4 differs from pull request most recent head bc7ede1. Consider uploading reports for the commit bc7ede1 to get more accurate results

@@            Coverage Diff             @@
##           master     #809      +/-   ##
==========================================
+ Coverage   49.03%   49.16%   +0.12%     
==========================================
  Files         210      210              
  Lines       15964    15965       +1     
  Branches     2547     2547              
==========================================
+ Hits         7828     7849      +21     
+ Misses       7634     7614      -20     
  Partials      502      502              

Flag	Coverage Δ
unittests	49.16% <100.00%> (+0.12%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmdet3d/datasets/pipelines/transforms_3d.py	90.41% <100.00%> (+0.01%)	⬆️
mmdet3d/models/segmentors/encoder_decoder.py	21.98% <0.00%> (+1.04%)	⬆️
mmdet3d/ops/group_points/group_points.py	33.33% <0.00%> (+2.15%)	⬆️
mmdet3d/models/decode_heads/paconv_head.py	56.25% <0.00%> (+12.50%)	⬆️
mmdet3d/ops/pointnet_modules/paconv_sa_module.py	50.79% <0.00%> (+22.22%)	⬆️

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