Remove several pieces of audit-related code

Summary: Ref T10978. This code (mostly related to the old ADD_AUDIT transaction and some to the "store English text in the database" audit reasons) is no longer reachable.

Test Plan:
Grepped for removed symbols:

• withAuditStatus
• getActionNameMap (unrelated callsites exist)
• getActionName (unrelated callsites exist)
• getActionPastTenseVerb
• addAuditReason
• getAuditReasons
• auditReasonMap

Also audited some commits.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10978

Differential Revision: https://secure.phabricator.com/D17267