feat: RuleTester supports processor

[mysticatea]

Link to rendered RFC

Summary

This RFC makes RuleTester class supporting processor option.

Related Issues

• https://github.com/eslint/rfcs/pull/25#issuecomment-499877621

[btmills]

@mysticatea if you have a moment to take a look at this: I'll be updating this RFC soon so we can use it to solve https://github.com/eslint/eslint/issues/14800. Before I do, were there any additional changes you had in mind for this that I should incorporate?

[eslint-github-bot[bot]]

Hi @mysticatea!, thanks for the Pull Request

The first commit message isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

• The commit message tag wasn't recognized. Did you mean "docs", "fix", or "feat"?
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[linux-foundation-easycla[bot]]

• :white_check_mark: Brandon Mills (07fd2eb473e9cfff5079af9c257e0ce3e84849e9)

• :x: - Toru Nagashima The commit (4af9338c3ec5f2355b2bc6c122c2bbe2e3b42150) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[btmills]

Since the original commit, 4af9338, was written under the old CLA, it is already covered. The CLA bot will report an error, but we can ignore it for that commit because all commits are covered by a CLA.

This is ready for review.