Add route update metrics tracking to PrefixHandler

- Add RecordIPv4Update and RecordIPv6Update to metrics package
- Add SetMetricsTracker method to PrefixHandler
- Track IPv4/IPv6 route updates when processing announcements
- Add GetMetricsTracker method to Streamer to expose metrics

internal/routewatch/app.go

@@ -118,6 +118,7 @@ func (rw *RouteWatch) Run(ctx context.Context) error {
 
 		// PrefixHandler maintains the prefixes and live_routes tables
 		rw.prefixHandler = NewPrefixHandler(rw.db, rw.logger)
+		rw.prefixHandler.SetMetricsTracker(rw.streamer.GetMetricsTracker())
 		rw.streamer.RegisterHandler(rw.prefixHandler)
 
 		// PeeringHandler maintains the asn_peerings table