[Refactor] Use MMCV MODEL_REGISTRY

[xvjiarui]

No description provided.

[codecov]

Codecov Report

Merging #5059 (7109722) into master (8a432d2) will decrease coverage by 0.67%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5059      +/-   ##
==========================================
- Coverage   66.71%   66.03%   -0.68%     
==========================================
  Files         259      261       +2     
  Lines       20269    20306      +37     
  Branches     3447     3466      +19     
==========================================
- Hits        13523    13410     -113     
- Misses       6019     6156     +137     
- Partials      727      740      +13     

Flag	Coverage Δ
unittests	66.00% <100.00%> (-0.69%)	⬇️

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

Impacted Files	Coverage Δ
mmdet/__init__.py	100.00% <100.00%> (ø)
mmdet/models/builder.py	93.10% <100.00%> (-0.84%)	⬇️
mmdet/models/dense_heads/yolo_head.py	51.59% <0.00%> (-10.36%)	⬇️
mmdet/models/roi_heads/bbox_heads/bbox_head.py	78.06% <0.00%> (-9.87%)	⬇️
mmdet/core/post_processing/bbox_nms.py	80.30% <0.00%> (-7.58%)	⬇️
mmdet/models/detectors/rpn.py	62.50% <0.00%> (-4.75%)	⬇️
mmdet/core/bbox/coder/tblr_bbox_coder.py	59.21% <0.00%> (-4.17%)	⬇️
mmdet/models/roi_heads/mask_heads/fcn_mask_head.py	69.41% <0.00%> (-2.37%)	⬇️
mmdet/models/roi_heads/test_mixins.py	54.06% <0.00%> (-1.91%)	⬇️
mmdet/models/dense_heads/anchor_head.py	86.08% <0.00%> (-1.74%)	⬇️
... and 25 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8a432d2...7109722. Read the comment docs.

[ZwwWayne]

This PR will be merged after the release of MMCV v1.3.2