[Docs] Add model statistics and polish some titles in configs README

[dreamerlin]

[codecov]

Codecov Report

Merging #4140 (78c63af) into master (f382ec8) will increase coverage by 0.14%.
The diff coverage is 61.76%.

@@            Coverage Diff             @@
##           master    #4140      +/-   ##
==========================================
+ Coverage   61.66%   61.80%   +0.14%     
==========================================
  Files         225      225              
  Lines       16654    16670      +16     
  Branches     2819     2823       +4     
==========================================
+ Hits        10269    10303      +34     
+ Misses       5884     5863      -21     
- Partials      501      504       +3     

Flag	Coverage Δ
unittests	61.76% <61.76%> (+0.13%)	⬆️

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

Impacted Files	Coverage Δ
mmdet/models/dense_heads/anchor_head.py	85.84% <ø> (ø)
mmdet/models/dense_heads/ssd_head.py	92.04% <ø> (ø)
mmdet/models/roi_heads/bbox_heads/bbox_head.py	85.16% <ø> (ø)
mmdet/core/bbox/coder/bucketing_bbox_coder.py	62.68% <50.00%> (+0.28%)	⬆️
mmdet/datasets/pipelines/transforms.py	72.70% <59.25%> (-0.49%)	⬇️
mmdet/core/bbox/coder/tblr_bbox_coder.py	21.66% <66.66%> (+1.32%)	⬆️
mmdet/core/bbox/coder/delta_xywh_bbox_coder.py	100.00% <100.00%> (ø)
mmdet/models/roi_heads/mask_heads/fcn_mask_head.py	75.97% <0.00%> (+1.29%)	⬆️
mmdet/models/roi_heads/mask_heads/maskiou_head.py	100.00% <0.00%> (+5.37%)	⬆️
mmdet/models/roi_heads/mask_scoring_roi_head.py	87.50% <0.00%> (+32.14%)	⬆️

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[ZwwWayne]

There are some weird items like Results and Models and common settings. Shall we skip these two items?

[ZwwWayne]

There are some weird items like Results and Models and common settings. Shall we skip these two items?

It seems that some readme.md of datasets is not correctly named. We can fix it later after merging this PR.

[dreamerlin]