DiscardingTaskGroup now shares some implementation with "Accumulating" TaskGroup

include/swift/ABI/TaskGroup.h

@@ -54,6 +54,14 @@ public:
 
   // Provide accessor for task group's status record
   TaskGroupTaskStatusRecord *getTaskRecord();
+
+  /// The group is a `TaskGroup` that accumulates results.
+  bool isAccumulatingResults() {
+    return !isDiscardingResults();
+  }
+
+  /// The group is a `DiscardingTaskGroup` that discards results.
+  bool isDiscardingResults();
 };
 
 } // end namespace swift