Standardizes API logging behavior

[djperrefort]

Standardizes the format, behavior, and treatment of different API log types (i.e., application, request, and audit logs).

Changes include:

• Adds the application setting CONFIG_AUDIT_RETENTION for enabling audit log rotation in the same fashion as request and application logs.
• Standardizes logs to use the timestamp for the record creation time.
• Uses less than or equal to instead of less than when rotating log files.
• Improves tests to individually validate the rotation of each log type.