R1:7087c0439a7f

Move the view of merged changes to "DiffusionCommitGraphView"

Summary: Ref T13552. When viewing a merge commit, merged changes are currently shown inline. Update this view to use the new "GraphView" rendering pipeline.

Test Plan:
- Viewed a merge commit, saw merges.
- Viewed history, profile page, etc.

Maniphest Tasks: T13552

Differential Revision: https://secure.phabricator.com/D21413