[ios] Ensure route settlement on iOS before handling DNS responses (#5360)

* Ensure route settlement on iOS before handling DNS responses to prevent bypassing the tunnel.

* add more logs

* rollback debug changes

* rollback  changes

* [client] Improve logging and add comments for iOS route settlement logic

- Switch iOS route settlement log level from Debug to Trace for finer control.
- Add clarifying comments for `waitForRouteSettlement` on non-iOS platforms.

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Co-authored-by: mlsmaycon <mlsmaycon@gmail.com>

client/internal/routemanager/dnsinterceptor/handler.go

@@ -351,6 +351,11 @@ func (d *DnsInterceptor) writeMsg(w dns.ResponseWriter, r *dns.Msg, logger *log.
 				logger.Errorf("failed to update domain prefixes: %v", err)
 			}
 
+			// Allow time for route changes to be applied before sending
+			// the DNS response (relevant on iOS where setTunnelNetworkSettings
+			// is asynchronous).
+			waitForRouteSettlement(logger)
+
 			d.replaceIPsInDNSResponse(r, newPrefixes, logger)
 		}
 	}