Add new metric "quality with no reference"

[ywchan2005]

What does this PR do?

Add new metric 'QNR' (quality with no reference)
(being part of #799 )

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

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📚 Documentation preview 📚: https://torchmetrics--2288.org.readthedocs.build/en/2288/

[codecov]

Codecov Report

Merging #2288 (9b0d153) into master (321a7a1) will increase coverage by 0%.
The diff coverage is 80%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #2288   +/-   ##
======================================
  Coverage      69%     69%           
======================================
  Files         303     305    +2     
  Lines       17058   17148   +90     
======================================
+ Hits        11760   11832   +72     
- Misses       5298    5316   +18     

[justusschock]

looking good already. few minor comments