Split ruff into multiple subcommands

[charliermarsh]

We could already support ruff format or ruff fmt or ruff rtrip (in Astor parlance). Soon there will be more tools and sub-commands, e.g., #423.

A few open questions:

• Do we want to move the core linting functionality to ruff check? Or leave it as a "default" sub-command? (I think the latter can cause a variety of ambiguities but it'd be nice to do something backwards compatible here.)
• Do we want to expose a dedicated ruff fix command in lieu of or in addition to --fix? Perhaps ruff fix applies fixes recursively.

[thejcannon]

Taking this a smidge further: one distinction I introduced to Pants is the distinction between fmt and fix. The former is safe to do on save, the latter isn't. The razor is something like removing imports. Not safe to do on save (as I'm still typing code and I save very often) but is safe to do in fix, which I'll issue manually.

We also have fix imply fmt, so users could decide which behavior they care about.

[not-my-profile]

@thejcannon Thanks, that's a very interesting idea! I think the relevant issue is rule applicability (#1997).