Add 'arc linters' to list available linters and status

Summary: Ref T2039. We're starting to get kind of a lot of linters; provide arc linters to help users review and understand them and construct .arclint files.

Test Plan:

Reviewers: btrahan, joshuaspence

Reviewed By: btrahan, joshuaspence

Subscribers: epriestley

Maniphest Tasks: T2039

Differential Revision: https://secure.phabricator.com/D9041