[improve](report) split agent batch tasks automaticlly (apache#43257)

to avoid the binary message size exceeds the thrift max message size
limitation

fe/fe-common/src/main/java/org/apache/doris/common/Config.java

@@ -1119,6 +1119,14 @@ public class Config extends ConfigBase {
     @ConfField(mutable = true, masterOnly = true)
     public static int report_queue_size = 100;
 
+    // if the number of report task in FE exceed max_report_task_num_per_rpc, then split it to multiple rpc
+    @ConfField(mutable = true, masterOnly = true, description = {
+            "重新发送 agent task 时，单次 RPC 分配给每个be的任务最大个数，默认值为10000个。",
+            "The maximum number of batched tasks per RPC assigned to each BE when resending agent tasks, "
+            + "the default value is 10000."
+    })
+    public static int report_resend_batch_task_num_per_rpc = 10000;
+
     /**
      * If set to true, metric collector will be run as a daemon timer to collect metrics at fix interval
      */

fe/fe-core/src/main/java/org/apache/doris/master/ReportHandler.java

@@ -524,7 +524,7 @@ private static void taskReport(long backendId, Map<TTaskType, Set<Long>> running
 
         List<AgentTask> diffTasks = AgentTaskQueue.getDiffTasks(backendId, runningTasks);
 
-        AgentBatchTask batchTask = new AgentBatchTask();
+        AgentBatchTask batchTask = new AgentBatchTask(Config.report_resend_batch_task_num_per_rpc);
         long taskReportTime = System.currentTimeMillis();
         for (AgentTask task : diffTasks) {
             // these tasks no need to do diff