[Bug][Broker] Fix bug that Broker's alive status is inconsistent in different FEs

In this CL, the isAlive field in FsBroker class will be persisted in metadata, to solve the
problem describe in ISSUE: #2989

Notice: this CL update FeMetaVersion to 73

fe/src/test/java/org/apache/doris/persist/FsBrokerTest.java

@@ -0,0 +1,109 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.apache.doris.persist;
+
+import org.apache.doris.catalog.FsBroker;
+import org.apache.doris.common.FeMetaVersion;
+import org.apache.doris.meta.MetaContext;
+import org.apache.doris.system.BrokerHbResponse;
+
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+
+public class FsBrokerTest {
+
+    private static String fileName1 = "./FsBrokerTest1";
+    private static String fileName2 = "./FsBrokerTest2";
+
+    @BeforeClass
+    public static void setup() {
+        MetaContext context = new MetaContext();
+        context.setMetaVersion(FeMetaVersion.VERSION_73);
+        context.setThreadLocalInfo();
+    }
+
+    @AfterClass
+    public static void tear() {
+        new File(fileName1).delete();
+        new File(fileName2).delete();
+    }
+
+    @Test
+    public void testHearbeatOk() throws Exception {
+        // 1. Write objects to file
+        File file = new File(fileName1);
+        file.createNewFile();
+        DataOutputStream dos = new DataOutputStream(new FileOutputStream(file));
+        
+        FsBroker fsBroker = new FsBroker("127.0.0.1", 8118);
+        long time = System.currentTimeMillis();
+        BrokerHbResponse hbResponse = new BrokerHbResponse("broker", "127.0.0.1", 8118, time);
+        fsBroker.handleHbResponse(hbResponse);
+        fsBroker.write(dos);
+        dos.flush();
+        dos.close();
+        
+        // 2. Read objects from file
+        DataInputStream dis = new DataInputStream(new FileInputStream(file));
+        
+        FsBroker readBroker = FsBroker.readIn(dis);
+        Assert.assertEquals(fsBroker.ip, readBroker.ip);
+        Assert.assertEquals(fsBroker.port, readBroker.port);
+        Assert.assertEquals(fsBroker.isAlive, readBroker.isAlive);
+        Assert.assertTrue(fsBroker.isAlive);
+        Assert.assertEquals(time, readBroker.lastStartTime);
+        Assert.assertEquals(-1, readBroker.lastUpdateTime);
+        dis.close();
+    }
+
+    @Test
+    public void testHeartbeatFailed() throws Exception {
+        // 1. Write objects to file
+        File file = new File(fileName2);
+        file.createNewFile();
+        DataOutputStream dos = new DataOutputStream(new FileOutputStream(file));
+
+        FsBroker fsBroker = new FsBroker("127.0.0.1", 8118);
+        long time = System.currentTimeMillis();
+        BrokerHbResponse hbResponse = new BrokerHbResponse("broker", "127.0.0.1", 8118, "got exception");
+        fsBroker.handleHbResponse(hbResponse);
+        fsBroker.write(dos);
+        dos.flush();
+        dos.close();
+
+        // 2. Read objects from file
+        DataInputStream dis = new DataInputStream(new FileInputStream(file));
+
+        FsBroker readBroker = FsBroker.readIn(dis);
+        Assert.assertEquals(fsBroker.ip, readBroker.ip);
+        Assert.assertEquals(fsBroker.port, readBroker.port);
+        Assert.assertEquals(fsBroker.isAlive, readBroker.isAlive);
+        Assert.assertFalse(fsBroker.isAlive);
+        Assert.assertEquals(-1, readBroker.lastStartTime);
+        Assert.assertEquals(-1, readBroker.lastUpdateTime);
+        dis.close();
+    }
+}