R1:71e9fb96b56e

Move more hunk loads into DifferentialHunkQuery

Summary: Ref T5179. Ref T4045. I want to move all hunk loads into DifferentialHunkQuery so I can make it do magical things where hunks come from multiple places, handle non-utf8 encodings properly, handle compression, archive into Files, and so on.

Test Plan: Viewed some revisions. Called `differential.getrawdiff`.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4045, T5179

Differential Revision: https://secure.