Update Differential diff view

Summary:
Ref T603.

• Primarily, this gets rid of a DifferentialRevisionListData callsite.
• Also modernize and clean up some UI stuff.

Test Plan:
{F48260}
{F48261}

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D6334