[Fix] OneCycleLrUpdaterHook adds total_steps

[MeowZheng]

Add total_steps, the total number of steps in the cycle. Note that if a value is not provided here, it will be the max_iter of runner.

[codecov]

Codecov Report

Merging #929 (ea03982) into master (d525cfd) will increase coverage by 0.02%.
The diff coverage is 64.70%.

❗ Current head ea03982 differs from pull request most recent head b4d783c. Consider uploading reports for the commit b4d783c to get more accurate results

@@            Coverage Diff             @@
##           master     #929      +/-   ##
==========================================
+ Coverage   65.40%   65.43%   +0.02%     
==========================================
  Files         151      151              
  Lines        9635     9648      +13     
  Branches     1775     1780       +5     
==========================================
+ Hits         6302     6313      +11     
  Misses       2986     2986              
- Partials      347      349       +2     

Flag	Coverage Δ
unittests	65.43% <64.70%> (+0.02%)	⬆️

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Impacted Files	Coverage Δ
mmcv/runner/hooks/logger/wandb.py	68.75% <40.00%> (-6.25%)	⬇️
mmcv/runner/hooks/lr_updater.py	65.78% <75.00%> (+1.39%)	⬆️

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[ZwwWayne]

lint failed.

[zhouzaida]

LGTM

[ZwwWayne]

CI failed