Migrate linter from pylint to ruff

[simon-mo]

The ruleset is roughly the same. ruff actually implement at lot more other rules that's super useful.

ruff yields 300x speedup for linting the files.

(base) xmo@simon-dev-l4x2:~/vllm$ time pylint vllm
real    0m10.963s
user    0m40.860s
sys     0m0.864s
(base) xmo@simon-dev-l4x2:~/vllm$ time ruff .

real    0m0.036s
user    0m0.007s
sys     0m0.052s

Currently I have disabled import sorting rules as the changes are going to be more drastic.

Additionally, ruff can automatically fixes the linting issue, saving developer time: https://docs.astral.sh/ruff/linter/#fixes

[zhuohan123]

Thanks for the work, Simon! LGTM in general. I have some dumb questions:

• Does this new style linter strictly follow google python style guide? If not, which standard does it follow?
• Does this linter forces line width at all? If so, what's the line width it forced?

[zhuohan123]

Nit: new line

[simon-mo]

Does this new style linter strictly follow google python style guide? If not, which standard does it follow?
It follows the styles checks we listed in pyproject.toml: pycodestyle, Pyflakes, flake8-bugbear, flake8-simplify, which I believes to have if not all overlap with Google style.

Does this linter forces line width at all? If so, what's the line width it forced?

No I explicitly turned it down by ignoring error E501. For long line with pure code, the formatter will be able to rewrite it into shorter line, or we can enforce it there. The long line with prompt, we are adding ignore anyway.