[augmentation] fix type hints for Output of Transform.forward

[tgy]

• fix Output type annotation, now reflecting that it can return y as a
  tuple of torch.Tensor
• define new Operation type hint, to annotate the Transform.operation
  attribute, to better check operation return types
• define Batch, Output and Operation as type aliases

[tgy]

seems that TypeAlias was not supported before Python 3.10, removed it

fixed the trailing whitespaces as well (flake8 should now pass, although we should switch to ruff - yes, saw the other PR)

[codecov]

Codecov Report

Merging #551 (d0539c4) into master (a5a2b04) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #551   +/-   ##
=======================================
  Coverage   83.73%   83.74%           
=======================================
  Files          63       63           
  Lines        4821     4822    +1     
=======================================
+ Hits         4037     4038    +1     
  Misses        784      784           

[tgy]

@bruAristimunha any idea why the Windows test are failing? seems it's failing why before running tests, during a pip install that fails

EDIT: i've tried to fix it in the workflow file. If you can re-run the CI build to check

[bruAristimunha]

Okay. Thank you @tgy for fixing the CI for the window. All good for me =)

[bruAristimunha]

Thank you for fix type @tgy