R1:b787d3ef0df7

Use standard infrastructure for Audit search indexing

Summary: Ref T4896.

Test Plan: Made an unusual comment, then found it by searching.

Reviewers: btrahan, joshuaspence

Reviewed By: btrahan, joshuaspence

Subscribers: epriestley

Maniphest Tasks: T4896

Differential Revision: https://secure.phabricator.com/D10110