isort: Support disabling sections with no-sections = true

[jelmer]

Summary

This adds a no-sections option for isort in the linter, similar to the no_sections option that exists in upstream isort (https://pycqa.github.io/isort/docs/configuration/options.html#no-sections)

This option puts all imports except for __future__ into the same section, and is mostly used by monorepos.

I've taken a bit of a leap in assuming that ruff wants to support the exact same option; more than happy to refactor if you'd prefer a different way of setting this up.

Fixes #8653

Test Plan

I've added a test and have run it on a large Python codebase that uses isort with --no-sections. The option is disabled by default.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[charliermarsh]

Thanks for getting involved! No objection to adding this, and no objection to using the same nomenclature and API as isort. Left a few small questions and comments, but should be able to get this merged relatively quickly.

[charliermarsh]

Thanks!