feat: add rotation option to both detection training scripts

[charlesmindee]

This PR adds the ability to train with rotated samples, by simply passing --rotation as an argument of the CLI detection training scripts.
The default rotation transformation performed on your training set is +-90°, and no rotation on the validation set, but this can be easily modified.

Here is how it renders for a batch of training samples:

Any feedback is welcome!

[codecov]

Codecov Report

Merging #765 (16c98a8) into main (c72da96) will decrease coverage by 0.04%.
The diff coverage is 92.00%.

@@            Coverage Diff             @@
##             main     #765      +/-   ##
==========================================
- Coverage   96.00%   95.95%   -0.05%     
==========================================
  Files         129      129              
  Lines        4807     4824      +17     
==========================================
+ Hits         4615     4629      +14     
- Misses        192      195       +3     

Flag	Coverage Δ
unittests	95.95% <92.00%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
doctr/utils/metrics.py	97.36% <ø> (ø)
doctr/transforms/functional/tensorflow.py	97.91% <83.33%> (-2.09%)	⬇️
doctr/utils/geometry.py	97.50% <87.50%> (-1.24%)	⬇️
doctr/datasets/detection.py	94.44% <100.00%> (+0.69%)	⬆️
...dels/detection/differentiable_binarization/base.py	93.52% <100.00%> (+0.03%)	⬆️
doctr/transforms/functional/pytorch.py	100.00% <100.00%> (ø)
doctr/transforms/modules/pytorch.py	97.67% <0.00%> (-2.33%)	⬇️

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[fg-mindee]

Thanks for the PR!
I raised a concern about the optimal order of transforms, cf my comments 👍

[fg-mindee]

Added a few comments!

[charlesmindee]

[fg-mindee]

Almost there!

[fg-mindee]

Isn't that gorgeous 😄
Great work @charlesmindee 👍

[charlesmindee]

I think for the train set it is OK, because if we don't rotate we don't want to use polygons and if we rotate we don't need polygons in the constructor because polygons are created in get_item when rotating boxes

[fg-mindee]

Looks good to me!