[fix](stats) Fix thread leaks when doing checkpoint (#27334)

fe/fe-core/src/main/java/org/apache/doris/statistics/AnalysisManager.java

@@ -248,7 +248,6 @@ public class AnalysisManager implements Writable {
         if (!Env.isCheckpointThread()) {
             this.taskExecutor = new AnalysisTaskExecutor(Config.statistics_simultaneously_running_task_num);
             this.statisticsCache = new StatisticsCache();
-            taskExecutor.start();
         }
     }
 

fe/fe-core/src/main/java/org/apache/doris/statistics/AnalysisTaskExecutor.java

@@ -32,7 +32,7 @@ import java.util.concurrent.PriorityBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
-public class AnalysisTaskExecutor extends Thread {
+public class AnalysisTaskExecutor {
 
     private static final Logger LOG = LogManager.getLogger(AnalysisTaskExecutor.class);
 
@@ -50,19 +50,12 @@ public class AnalysisTaskExecutor extends Thread {
                     TimeUnit.DAYS, new LinkedBlockingQueue<>(),
                     new BlockedPolicy("Analysis Job Executor", Integer.MAX_VALUE),
                     "Analysis Job Executor", true);
+            cancelExpiredTask();
         } else {
             executors = null;
         }
     }
 
-    @Override
-    public void run() {
-        if (Env.isCheckpointThread()) {
-            return;
-        }
-        cancelExpiredTask();
-    }
-
     private void cancelExpiredTask() {
         String name = "Expired Analysis Task Killer";
         Thread t = new Thread(this::doCancelExpiredJob, name);

fe/fe-core/src/main/java/org/apache/doris/statistics/StatisticsCollector.java

@@ -40,7 +40,6 @@ public abstract class StatisticsCollector extends MasterDaemon {
     public StatisticsCollector(String name, long intervalMs, AnalysisTaskExecutor analysisTaskExecutor) {
         super(name, intervalMs);
         this.analysisTaskExecutor = analysisTaskExecutor;
-        analysisTaskExecutor.start();
     }
 
     @Override