MeanAveragePrecision backend

[SkafteNicki]

What does this PR do?

Fixes #1153
Fixes #2035
Adds a backend argument to MeanAveragePrecision. The official pycocotools implementation we use is flawed as there are certain corner cases were the implementation does not work. Sadly the implementation is not really maintained any more. However, it is still considered the "official" implementation and therefore we cannot do so much about this.

This PR adds the possibility of other backends for computation, starting with https://github.com/MiXaiLL76/faster_coco_eval which is a faster version and fixes at least the corner case identified in the linked issue. I still think we need to keep pycocotools as the default backend even if all the testing I have done shows that the two backends produce identical results.

The goal for the future would be to reintroduce our old pytorch implementation with backend="pytorch"

Before submitting

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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--2034.org.readthedocs.build/en/2034/

[codecov]

Codecov Report

Merging #2034 (6e3930c) into master (1caaf28) will increase coverage by 0%.
The diff coverage is 93%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #2034   +/-   ##
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  Coverage      87%     87%           
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  Files         285     285           
  Lines       15993   16021   +28     
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+ Hits        13871   13916   +45     
+ Misses       2122    2105   -17     

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