net: add LogIP() helper, use in net_processing

src/net.h

@@ -947,6 +947,14 @@ public:
 
     std::string ConnectionTypeAsString() const { return ::ConnectionTypeAsString(m_conn_type); }
 
+    /**
+     * Helper function to optionally log the IP address.
+     *
+     * @param[in] log_ip whether to include the IP address
+     * @return " peeraddr=..." or ""
+     */
+    std::string LogIP(bool log_ip) const;
+
     /**
      * Helper function to log disconnects.
      *