R1:25ee2d4508d8

Rename `DifferentialHunk` subclasses for consistency

Summary: Ref T5655.

Test Plan: `arc lint`

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T5655

Differential Revision: https://secure.phabricator.com/D11470