[Feature] Support CPU training

[ckkelvinchan]

Reference: open-mmlab/mmdetection#7016

[codecov]

Codecov Report

Merging #720 (9faf1fd) into master (933220a) will increase coverage by 0.12%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #720      +/-   ##
==========================================
+ Coverage   81.80%   81.92%   +0.12%     
==========================================
  Files         211      212       +1     
  Lines       11896    11955      +59     
  Branches     1912     1922      +10     
==========================================
+ Hits         9731     9794      +63     
+ Misses       1869     1862       -7     
- Partials      296      299       +3     

Flag	Coverage Δ
unittests	81.90% <0.00%> (+0.12%)	⬆️

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

Impacted Files	Coverage Δ
mmedit/apis/train.py	18.00% <0.00%> (ø)
mmedit/apis/__init__.py	100.00% <0.00%> (ø)
mmedit/apis/video_interpolation_inference.py	91.22% <0.00%> (ø)
...t/models/video_interpolators/basic_interpolator.py	97.32% <0.00%> (+0.02%)	⬆️
mmedit/models/video_interpolators/cain.py	100.00% <0.00%> (+4.00%)	⬆️
mmedit/apis/matting_inference.py	39.02% <0.00%> (+19.51%)	⬆️

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[wangruohui]

Should we also modify somewhere in the documents ?

[ckkelvinchan]

Should we also modify somewhere in the documents ?

Let me check