Allow `ArcanistPhutilXHPASTLinter` to be configured from `.arclint`.

Summary: Currently, `PhabricatorLintEngine` configures the `ArcanistPhutilXHPASTLinter` linter. In order to use `.arclint` instead, we need to expose the `ArcanistPhutilXHPASTLinter` configuration to the `.arclint` format.

Test Plan: See D9064.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T2039

Differential Revision: https://secure.phabricator.com/D9066