Shuffle DNS records before propagating to LoadBalancer (#2673)

Motivation:

If multiple client instances receive identical DNS records set, they
will start connecting to the same upstream instances because the
collection is always sorter.

Modifications:

- Shuffle the list before propagating to the load balancer;

Result:

More uniform distribution of the initial connections.

servicetalk-dns-discovery-netty/src/main/java/io/servicetalk/dns/discovery/netty/DefaultDnsClient.java

@@ -68,6 +68,7 @@
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
@@ -846,6 +847,10 @@ private void handleResolveDone0(final Future<DnsAnswer<T>> addressFuture,
                             cancellableForQuery = null;
                         }
                         try {
+                            // Shuffle events to avoid multiple clients connecting to the same upstream IP address if
+                            // they receive identical result set from DNS.
+                            Collections.shuffle(events);
+
                             LOGGER.debug("{} sending events for {} (size={}, TTL={}s): {}.",
                                     DefaultDnsClient.this, AbstractDnsPublisher.this, events.size(),
                                     NANOSECONDS.toSeconds(ttlNanos), events);