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