Add http_referer field to system.query_log and system.processes

Why it matters

This feature allows users to track the HTTP referer header associated with queries, providing greater insight into the origin of requests made to ClickHouse. It helps in auditing, debugging, and monitoring query sources more effectively.

How to use it

The http_referer field is automatically populated in system.query_log, system.processes, and similar tables for queries coming over HTTP. Users can query these system tables to view the referer information without additional configuration.