Add toString() for RemoteConnectionInfo and ModeInfo impls (#138851)

Adds generated toString() methods for RemoteConnectionInfo
and the ModeInfo implementations to support debugging of
assertions.

Relates: ES-13292

Author: JeremyDahlgren

server/src/main/java/org/elasticsearch/transport/ProxyConnectionStrategy.java

@@ -305,5 +305,21 @@ public boolean equals(Object o) {
         public int hashCode() {
             return Objects.hash(address, serverName, maxSocketConnections, numSocketsConnected);
         }
+
+        @Override
+        public String toString() {
+            return "ProxyModeInfo{"
+                + "address='"
+                + address
+                + '\''
+                + ", serverName='"
+                + serverName
+                + '\''
+                + ", maxSocketConnections="
+                + maxSocketConnections
+                + ", numSocketsConnected="
+                + numSocketsConnected
+                + '}';
+        }
     }
 }

server/src/main/java/org/elasticsearch/transport/RemoteConnectionInfo.java

@@ -121,6 +121,23 @@ public int hashCode() {
         return Objects.hash(modeInfo, initialConnectionTimeout, clusterAlias, skipUnavailable, hasClusterCredentials);
     }
 
+    @Override
+    public String toString() {
+        return "RemoteConnectionInfo{"
+            + "modeInfo="
+            + modeInfo
+            + ", initialConnectionTimeout="
+            + initialConnectionTimeout
+            + ", clusterAlias='"
+            + clusterAlias
+            + '\''
+            + ", skipUnavailable="
+            + skipUnavailable
+            + ", hasClusterCredentials="
+            + hasClusterCredentials
+            + '}';
+    }
+
     public interface ModeInfo extends ToXContentFragment, Writeable {
 
         boolean isConnected();

server/src/main/java/org/elasticsearch/transport/SniffConnectionStrategy.java

@@ -537,5 +537,17 @@ public boolean equals(Object o) {
         public int hashCode() {
             return Objects.hash(seedNodes, maxConnectionsPerCluster, numNodesConnected);
         }
+
+        @Override
+        public String toString() {
+            return "SniffModeInfo{"
+                + "seedNodes="
+                + seedNodes
+                + ", maxConnectionsPerCluster="
+                + maxConnectionsPerCluster
+                + ", numNodesConnected="
+                + numNodesConnected
+                + '}';
+        }
     }
 }