Fix child device

[SkafteNicki]

Before submitting

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• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

Fixes #531
Currently if a metric is a child of a module, the device property (only the property, the metric states are still correctly updated) of the metric will not get properly update (only if .cuda(), .cpu(), to() is directly called on the metric) when calling .cuda() on the module. This PR fixes it.

PR review

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[codecov]

Codecov Report

Merging #542 (80de7c2) into master (f9d7d5f) will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #542   +/-   ##
=====================================
  Coverage      95%    95%           
=====================================
  Files         132    132           
  Lines        4680   4660   -20     
=====================================
- Hits         4461   4444   -17     
+ Misses        219    216    -3     

[cowwoc]

@SkafteNicki Thank you for working on this fix!

[SkafteNicki]

@cowwoc if you have the time, please confirm that this fixes your original issue :]

[an1lam]

Thanks @SkafteNicki!