Restore unintentionally removed RoundRobinLoadBalancerFactory API (#…

…2849)

Motivation:

japicmp report:
```
***! MODIFIED CLASS: PUBLIC FINAL io.servicetalk.loadbalancer.RoundRobinLoadBalancerFactory  (not serializable)
        ===  CLASS FILE FORMAT VERSION: 52.0 <- 52.0
        ===  UNCHANGED SUPERCLASS: java.lang.Object (<- java.lang.Object)
        ---! REMOVED METHOD: PUBLIC(-) io.servicetalk.client.api.LoadBalancer newLoadBalancer(io.servicetalk.concurrent.api.Publisher, io.servicetalk.client.api.ConnectionFactory, java.lang.String)
```

servicetalk-loadbalancer/src/main/java/io/servicetalk/loadbalancer/RoundRobinLoadBalancerFactory.java

@@ -78,6 +78,15 @@ public <T extends C> LoadBalancer<T> newLoadBalancer(
                 linearSearchSpace, healthCheckConfig);
     }
 
+    @Override
+    public LoadBalancer<C> newLoadBalancer(
+            final Publisher<? extends Collection<? extends ServiceDiscovererEvent<ResolvedAddress>>> eventPublisher,
+            final ConnectionFactory<ResolvedAddress, C> connectionFactory,
+            final String targetResource) {
+        return new RoundRobinLoadBalancer<>(id, targetResource, eventPublisher, connectionFactory,
+                linearSearchSpace, healthCheckConfig);
+    }
+
     @Override
     public ExecutionStrategy requiredOffloads() {
         // We do not block