Move metrics_to_scalars to a dedicated utilities file

[ananthsub]

What does this PR do?

Similar to #6834 to simplify the trainer class inheritance. This doesn't need to be a mixin since it doesn't use any trainer state. It's a pure function which we can put into a utilities file to avoid false dependencies on the trainer class

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[pep8speaks]

Hello @ananthsub! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-04-23 19:09:37 UTC

[codecov]

Codecov Report

Merging #7180 (6c1ced4) into master (c502e47) will decrease coverage by 5%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #7180    +/-   ##
=======================================
- Coverage      92%     87%    -5%     
=======================================
  Files         197     198     +1     
  Lines       12622   12717    +95     
=======================================
- Hits        11631   11040   -591     
- Misses        991    1677   +686     

[carmocca]

Thanks for cleaning this

[carmocca]

Can you keep this TODO?

[tchaton]

LGTM !