Switch formatting from black+isort to µfmt (black+µsort)

[amyreese]

Description:

This switches linting, formatting, and pre-commit checks from using black and isort directly to using µfmt, which runs µsort and black as an atomic formatting step. This matches what torchvision uses (pytorch/vision#4384).

Covered files were formatted using ./tests/run_code_style.sh fmt and pre-commit run validated the results.

Check list:

• New tests are added (if a new feature is added)
• New doc strings: description and/or example code are in RST format
• Documentation is updated (if required)

[vfdev-5]

@jreese thanks for the PR ! Yes, ufmt works well in torchvision and maintainers are rather happy with it.
I left a comment and let me see what other maintainers think about the change as code formatting could be rather opinionated :)

[amyreese]

Rebased onto latest and unified on using usort diff.

[vfdev-5]

Thanks @jreese !