Fix tie breaking in ndcg metric

[SkafteNicki]

What does this PR do?

Fixes #2022
In the issue it was identified that the overall problem is that our implementation of ndcg currently cannot deal with tie breaks of scores. PR fixes this.

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• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

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📚 Documentation preview 📚: https://torchmetrics--2031.org.readthedocs.build/en/2031/

[codecov]

Codecov Report

Merging #2031 (e94afaa) into master (163b0aa) will decrease coverage by 51%.
Report is 1 commits behind head on master.
The diff coverage is 37%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #2031     +/-   ##
========================================
- Coverage      87%     36%    -51%     
========================================
  Files         283     285      +2     
  Lines       15934   15993     +59     
========================================
- Hits        13832    5691   -8141     
- Misses       2102   10302   +8200     

[SkafteNicki]

@lucadiliello could you please review as you are the expert on retrieval?

[lucadiliello]

I think this issue may also affect other retrieval metrics. The problem with other retrieval metrics is that definitions are not really standardized between Wikipedia and slides of university courses. I mean that the general definition is the same, but the behavior in corner cases like this one is not well defined.

I'm currently on vacation, I will try to review the PR once I'm in front of my pc.

[Borda]

I'm currently on vacation, I will try to review the PR once I'm in front of my pc.

cool, @lucadiliello let us know when you ll check and and ideally if all fine approve this PR :)

[Borda]

@lucadiliello pls mind checking it ^^

[lucadiliello]

LGTM