Fix Eclipse specific compilation issue (#37419)

Without pulling out the supplier function to the enclosing class, Eclipse 4.8
complains with the following error "No enclosing instance of type
CoordinatorTests.Cluster is available due to some intermediate constructor
invocation"

server/src/test/java/org/elasticsearch/cluster/coordination/CoordinatorTests.java

@@ -19,6 +19,7 @@
 package org.elasticsearch.cluster.coordination;
 
 import com.carrotsearch.randomizedtesting.RandomizedContext;
+
 import org.apache.logging.log4j.CloseableThreadContext;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -90,10 +91,10 @@
 import static org.elasticsearch.cluster.coordination.CoordinationStateTests.clusterState;
 import static org.elasticsearch.cluster.coordination.CoordinationStateTests.setValue;
 import static org.elasticsearch.cluster.coordination.CoordinationStateTests.value;
+import static org.elasticsearch.cluster.coordination.Coordinator.PUBLISH_TIMEOUT_SETTING;
 import static org.elasticsearch.cluster.coordination.Coordinator.Mode.CANDIDATE;
 import static org.elasticsearch.cluster.coordination.Coordinator.Mode.FOLLOWER;
 import static org.elasticsearch.cluster.coordination.Coordinator.Mode.LEADER;
-import static org.elasticsearch.cluster.coordination.Coordinator.PUBLISH_TIMEOUT_SETTING;
 import static org.elasticsearch.cluster.coordination.CoordinatorTests.Cluster.DEFAULT_DELAY_VARIABILITY;
 import static org.elasticsearch.cluster.coordination.ElectionSchedulerFactory.ELECTION_BACK_OFF_TIME_SETTING;
 import static org.elasticsearch.cluster.coordination.ElectionSchedulerFactory.ELECTION_DURATION_SETTING;
@@ -1101,6 +1102,9 @@ class Cluster {
         private final Set<String> blackholedNodes = new HashSet<>();
         private final Map<Long, ClusterState> committedStatesByVersion = new HashMap<>();
 
+        private final Function<DiscoveryNode, PersistedState> defaultPersistedStateSupplier = localNode -> new MockPersistedState(0L,
+                clusterState(0L, 0L, localNode, VotingConfiguration.EMPTY_CONFIG, VotingConfiguration.EMPTY_CONFIG, 0L));
+
         Cluster(int initialNodeCount) {
             this(initialNodeCount, true);
         }
@@ -1533,9 +1537,7 @@ class ClusterNode {
             private ClusterStateApplyResponse clusterStateApplyResponse = ClusterStateApplyResponse.SUCCEED;
 
             ClusterNode(int nodeIndex, boolean masterEligible) {
-                this(nodeIndex, createDiscoveryNode(nodeIndex, masterEligible),
-                    localNode -> new MockPersistedState(0L,
-                        clusterState(0L, 0L, localNode, VotingConfiguration.EMPTY_CONFIG, VotingConfiguration.EMPTY_CONFIG, 0L)));
+                this(nodeIndex, createDiscoveryNode(nodeIndex, masterEligible), defaultPersistedStateSupplier);
             }
 
             ClusterNode(int nodeIndex, DiscoveryNode localNode, Function<DiscoveryNode, PersistedState> persistedStateSupplier) {