[Enhancement] Pass custom_hooks to MMCV

[gaotongxiao]

Modifications

Transfer the processing steps of custom_hooks to MMCV.

BC Breaking

None. MMCV 1.3.4 started to support this argument whereas MMOCR's minimum version requirement is 1.3.8.

[codecov]

Codecov Report

Merging #609 (3387b4b) into main (53b050b) will increase coverage by 0.07%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             main     #609      +/-   ##
==========================================
+ Coverage   84.86%   84.93%   +0.07%     
==========================================
  Files         143      143              
  Lines        9816     9806      -10     
  Branches     1420     1418       -2     
==========================================
- Hits         8330     8329       -1     
+ Misses       1158     1149       -9     
  Partials      328      328              

Flag	Coverage Δ
unittests	84.93% <50.00%> (+0.07%)	⬆️

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

Impacted Files	Coverage Δ
mmocr/apis/train.py	17.64% <50.00%> (+0.98%)	⬆️

---

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 53b050b...3387b4b. Read the comment docs.