Move most Differetial keyboard shortcuts into DiffChangesetList

Summary: Ref T12616. This moves most keyboard shortcuts into DiffChangesetList. It breaks some shortcuts that I plan to restore later, noted in T12616 (toggle file, edit inline, reply to inline), since I think ripping them out now and rebuilding them in a little bit will make things much simpler.

Test Plan:

• Used j, k, n, p, J, K shortcuts to navigate a revision.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12616

Differential Revision: https://secure.phabricator.com/D17859