1. log client_flow_id into ClientSession

2. In NS, passing the saved advertising flow id into NC so the client_flow_id in receiver side could be the same as the NS one, which could have the correct records mapping between the NS and NC.

PiperOrigin-RevId: 582876537

internal/proto/analytics/connections_log.proto

@@ -63,6 +63,9 @@ message ConnectionsLog {
 
     // Zero or more StrategySessions.
     repeated StrategySession strategy_session = 2;
+
+    // The client session flow id.
+    optional int64 client_flow_id = 3 /* type = ST_SESSION_ID */;
   }
 
   // One round of a particular Strategy done by a client.