Move the "ragged classtree edge" linter rule to `ArcanistPhutilXHPASTLinter`.

Summary: This linter rule is very specific to the Phabricator and it is unlikely that it is being used elsewhere. We should move it to `ArcanistPhutilXHPASTLinter`, where other Phabricator-specific linting code lives.

Test Plan: Moved the corresponding test case.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9590