Hide direct accesses to Audit inline comment table behind API

Summary: Ref T4896. Move all direct accesses to the inline comment table behind a small amount of API to make it easier to migrate the table.

Test Plan:
  - Grepped for `PhabricatorAuditInlineComment`.
  - Grepped for `audit_inlinecomment`.
  - Created a draft comment.
  - Previewed a draft comment.
  - Reloaded page, still saw draft.
  - Viewed standalone, still saw draft.
  - Made comment, inline published.
  - Added a draft, saw both.
  - Edited inline comment.
  - Reindexed commit.
  - Searched for unique word in published comment, found commit.
  - Searched for unique word in draft comment, no results.

Reviewers: btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T4896

Differential Revision: https://secure.phabricator.com/D10016