[IMPROVED] Don't log R1 ephemerals in clustered environments (#7003)

```
[INF] JetStream cluster new consumer leader for '$G > KV_bucket > p7eMKZwR'
```
This logline is often either confusing or annoying. It happens for every
R1 ephemeral that's (re)created and may result in lots of noise when
using many KV watchers for example. This line is purely a side-effect of
running in a clustered environment, in a standalone server this wouldn't
happen, and doesn't mean much because the leader of an R1 ephemeral is
always known and will not change.

Still sending the advisory though, to ensure we stay compatible.

Signed-off-by: Maurice van Veen <[email protected]>

Author: neilalexander

server/jetstream_cluster.go

@@ -5223,7 +5223,14 @@ func (js *jetStream) processConsumerLeaderChange(o *consumer, isLeader bool) err
 	}
 
 	if isLeader {
-		s.Noticef("JetStream cluster new consumer leader for '%s > %s > %s'", ca.Client.serviceAccount(), streamName, consumerName)
+		// Only log if the consumer is replicated and/or durable.
+		// Logging about R1 ephemerals, like KV watchers, is mostly noise since the leader will always be known.
+		o.mu.RLock()
+		isReplicated, durable := o.node != nil, o.isDurable()
+		o.mu.RUnlock()
+		if isReplicated || durable {
+			s.Noticef("JetStream cluster new consumer leader for '%s > %s > %s'", ca.Client.serviceAccount(), streamName, consumerName)
+		}
 		s.sendConsumerLeaderElectAdvisory(o)
 	} else {
 		// We are stepping down.