Add --lint=fix and --lint=warn to buildifier

[nlou9]

Add flag --lint=fix and --lint=warn to the buildifier.
https://github.com/bazelbuild/buildtools/blob/main/WARNINGS.md

---

Changes are visible to end-users: yes/no

• Searched for relevant documentation and updated as needed: yes/no
• Breaking change (forces users to change their own code or config): yes/no
• Suggested release notes appear below: yes/no

Test plan

• Covered by existing test cases
• New test cases added
• Manual testing; please provide instructions so we can reproduce:

[CLAassistant]

All committers have signed the CLA.

[alexeagle]

This looks incorrect because Buildifier is run here as a formatter, not a linter. See the README for the design of how they are treated separately

[nlou9]

thanks, I will move the buildifier linter part to the lint section.

[alexeagle]

We don't have a buildifier linter here yet, because the linting is based on an aspect walking the dependency graph, and there are typically no targets that list BUILD and *.bzl files as their sources. I'm not sure if it's worth introducing bzl_library in every package.

[nlou9]

Instead of adding a liner for Buildifier, in short term I wonder if we could allow users to extend CHECK_FLAGS and FIX_FLAGS. I think this might also be useful in other scenarios.

[alexeagle]

#377

[alexeagle]

closing as dupe of #377 - thanks for helping out!