[Feature](Job)Support scheduler job (#21916)

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

@@ -1520,6 +1520,9 @@ public class Config extends ConfigBase {
     @ConfField
     public static boolean enable_pipeline_load = false;
 
+    @ConfField
+    public static int scheduler_job_task_max_num = 10;
+
     // enable_workload_group should be immutable and temporarily set to mutable during the development test phase
     @ConfField(mutable = true, expType = ExperimentalType.EXPERIMENTAL)
     public static boolean enable_workload_group = false;