[Bug](profile) fix wrong 'Total Instances Num' in profile

fe/fe-core/src/main/java/org/apache/doris/qe/NereidsCoordinator.java

@@ -392,7 +392,7 @@ public Map<String, Integer> getBeToInstancesNum() {
             for (MultiFragmentsPipelineTask beTasks : executionTask.getChildrenTasks().values()) {
                 TNetworkAddress brpcAddress = beTasks.getBackend().getBrpcAddress();
                 String brpcAddrString = brpcAddress.hostname.concat(":").concat("" + brpcAddress.port);
-                result.put(brpcAddrString, beTasks.getChildrenTasks().size());
+                result.put(brpcAddrString, beTasks.getInstanceNum());
             }
         }
         return result;

fe/fe-core/src/main/java/org/apache/doris/qe/runtime/AbstractRuntimeTask.java

@@ -33,6 +33,12 @@ public void execute() throws Throwable {
         }
     }
 
+    public Integer getInstanceNum() {
+        return childrenTasks.allTasks().stream()
+                .mapToInt(Child::getInstanceNum)
+                .sum();
+    }
+
     public Map<ChildId, Child> getChildrenTasks() {
         return childrenTasks.allTaskMap();
     }

fe/fe-core/src/main/java/org/apache/doris/qe/runtime/SingleFragmentPipelineTask.java

@@ -82,6 +82,10 @@ public int getFragmentId() {
         return fragmentId;
     }
 
+    public Integer getInstanceNum() {
+        return instanceIds.size();
+    }
+
     public List<FragmentInstanceInfo> buildFragmentInstanceInfo() {
         TNetworkAddress address = new TNetworkAddress(backend.getHost(), backend.getBePort());
         List<FragmentInstanceInfo> infos = Lists.newArrayListWithCapacity(instanceIds.size());