[client] Serialize Android tunnel reconfiguration callbacks

The Android route notifier and the DNS search-domain notifier both
delivered OnNetworkChanged from a fire-and-forget goroutine per update.
Two updates in quick succession could reach the Java side reordered:
the TUN rebuild handler applies them in arrival order and compares
against the last applied parameters, so a stale route set delivered
last won as the final TUN state. This is the same reordering hazard
fixed for iOS in #6454.

Wrap the Android network change listener into the shared tunnelnotifier
FIFO introduced in #6870, the same way RunOniOS does, and deliver both
notifiers synchronously into it. Enqueueing is non-blocking, a single
delivery goroutine preserves order, and calls into Java never overlap.

Also stop hasRouteDiff from sorting the notifier's shared route slices
in place; compare sorted copies instead.

client/internal/dns/notifier.go

@@ -51,7 +51,5 @@ func (n *notifier) notify() {
 		return
 	}
 
-	go func(l listener.NetworkChangeListener) {
-		l.OnNetworkChanged("")
-	}(n.listener)
+	n.listener.OnNetworkChanged("")
 }