Apply normal Audit actions directly with Transaction editor

Summary: Ref T4896. This converts the last "CommentEditor" to a transaction editor and removes a large part of the old code.

Test Plan:
  - Added comments.
  - Accepted / added auditors.
  - Added inline comments.

Reviewers: joshuaspence, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4896

Differential Revision: https://secure.phabricator.com/D10128