Make inline comment preview and submission mostly work on EditEngine

Summary: Ref T11114. This comments nearly working on EditEngine. Only significant issue I caught is that the "View" link doesn't render properly because it depends on JS which is tricky to hook up. I'll clean that up in a future diff.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11114

Differential Revision: https://secure.phabricator.com/D17116