MeanAveragePrecision box and segm at same time

[SkafteNicki]

What does this PR do?

Fixes #1905

Make it possible to extract mean average precision for both box and segmentation input at the same time. This is a larger refactor of the internals of the map metric, but it should make it easier to add support for keypoint detection (#1361) in the future.

I am fairly confident that this does not break backwards compatibility in any way as all original tests are passing without any changes.

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--1928.org.readthedocs.build/en/1928/

[vsuryamurthy]

Perfect, thanks for this change!

[codecov]

Codecov Report

Merging #1928 (d5b9080) into master (6aa6183) will decrease coverage by 48%.
Report is 1 commits behind head on master.
The diff coverage is 95%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1928     +/-   ##
========================================
- Coverage      86%     39%    -48%     
========================================
  Files         266     266             
  Lines       15205   15280     +75     
========================================
- Hits        13148    5941   -7207     
- Misses       2057    9339   +7282     

[Borda]

@SkafteNicki, mind checking the collision withe the prefix PR? 🦩