Add DvcliveLoggerHook

[daavoo]

Motivation

I would like to use https://dvc.org/doc/dvclive as a Logger.

Modification

I added a new LoggerHook child to the HOOKS registry.

Use cases (Optional)

Logging training parameters with dvclive (https://github.com/iterative/dvclive)

[codecov]

Codecov Report

Merging #1075 (446eee0) into master (d212bd5) will increase coverage by 0.04%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master    #1075      +/-   ##
==========================================
+ Coverage   65.72%   65.77%   +0.04%     
==========================================
  Files         157      158       +1     
  Lines       10092    10115      +23     
  Branches     1828     1831       +3     
==========================================
+ Hits         6633     6653      +20     
- Misses       3113     3115       +2     
- Partials      346      347       +1     

Flag	Coverage Δ
unittests	65.77% <87.50%> (+0.04%)	⬆️

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Impacted Files	Coverage Δ
mmcv/runner/__init__.py	100.00% <ø> (ø)
mmcv/runner/hooks/logger/dvclive.py	86.36% <86.36%> (ø)
mmcv/runner/hooks/__init__.py	100.00% <100.00%> (ø)
mmcv/runner/hooks/logger/__init__.py	100.00% <100.00%> (ø)

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[zhouzaida]

LGTM