Chore: refactor directive comment processing

[not-an-aardvark]

What is the purpose of this pull request? (put an "X" next to item)

[x] Other, please explain:

What changes did you make? (Give an overview)

This makes a few improvements to directive comment processing in linter.js:

• Avoids internally adding some unrelated properties to config objects
• Fixes some code duplication
• Avoids some unnecessary branches

Note: it might be useful to view the diff with whitespace changes omitted (link)

Is there anything you'd like reviewers to focus on?

Nothing in particular

[ilyavolodin]

I know this is not directly related, but I would love to move comment processing out of linter completely. They are not related, and comments processing shares a lot of logic with config processing.

[not-an-aardvark]

I agree. At the moment the function's API is still a bit cluttered because the function gets a lot of information from various places, but maybe it can be simplified and extracted.