prefilter audit records in query engine

Three parts:

• Use prefiltering info to filter based on enabled audit record numbers and user whitelist. (DONE,  -MB-26625-)
• Retrieve filtering settings from ns_server. (DONE)
• Inform audit demon prefiltering is being done in query engine. (DONE)

Audit demon design doc: https://docs.google.com/document/d/18T9UquZOqz0acQycGyXZ9wh7DBq5nMoo900Tz_mrzl0/edit#heading=h.5berxaq3ahos