support coordinator epoch

Author: zcoo

fluss-server/src/main/java/org/apache/fluss/server/coordinator/CoordinatorLeaderElection.java

@@ -128,7 +128,6 @@ private void relinquishLeadership() {
         try {
             leaderLatch.close();
             server.closeAsync();
-            leaderLatch.start();
         } catch (Exception e) {
         }
     }

fluss-server/src/main/java/org/apache/fluss/server/coordinator/CoordinatorServer.java

@@ -55,9 +55,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
-import java.util.Map;
 import java.util.Optional;
-import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;

fluss-server/src/main/java/org/apache/fluss/server/zk/ZooKeeperClient.java

@@ -56,7 +56,6 @@
 import org.apache.fluss.server.zk.data.ZkData.BucketSnapshotIdZNode;
 import org.apache.fluss.server.zk.data.ZkData.BucketSnapshotsZNode;
 import org.apache.fluss.server.zk.data.ZkData.ConfigEntityZNode;
-import org.apache.fluss.server.zk.data.ZkData.CoordinatorZNode;
 import org.apache.fluss.server.zk.data.ZkData.DatabaseZNode;
 import org.apache.fluss.server.zk.data.ZkData.DatabasesZNode;
 import org.apache.fluss.server.zk.data.ZkData.LakeTableZNode;