Refactor panoptic quality

[marcocaccin]

What does this PR do?

Preparation work for #1591: breaks apart the big messy update() function, and moves all the helper functions to a new src/torchmetrics/functional/detection/_panoptic_quality_common.py file.

To make the review a lot simpler, the PR contains 2 commits: I suggest to look at the first commit 7cbf54b which contains all the new code and it can be diff'd against master, whereas the 2nd commit d873aab is doing nothing else than moving code around (edit, there'll be a 3rd because I initially borked the type annotations and found out that mypy doesn't run on pre-commit).

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 🙃

[codecov]

Codecov Report

Merging #1596 (36191bf) into master (21b23b6) will decrease coverage by 51%.
The diff coverage is 96%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1596     +/-   ##
========================================
- Coverage      88%     38%    -51%     
========================================
  Files         225     226      +1     
  Lines       11938   11952     +14     
========================================
- Hits        10555    4510   -6045     
- Misses       1383    7442   +6059     

[marcocaccin]

Not sure how to interpret the codecov failure, the PR doesn't add any "new" code. Is it a CI glitch? Should I do something about it?

[Borda]

I suggest to look at the first commit 7cbf54b which contains all the new code and it can be diff'd against master

let's just stay with this one commit pls 🦦

[Borda]

Not sure how to interpret the codecov failure, the PR doesn't add any "new" code. Is it a CI glitch? Should I do something about it?

it is a sanity check that the new code is covered, but it also has some false negative alarms when the coverage change is almost zero...