fix(pivot): Extract hierarchy from original leaf records.

Author: MKirova

projects/igniteui-angular/src/lib/data-operations/pivot-strategy.ts

@@ -50,8 +50,9 @@ export class PivotRowDimensionsStrategy implements IPivotDimensionStrategy {
                 const newData = [...data];
                 for (let i = 0; i < newData.length; i++) {
                     const currData = newData[i][prevDim.memberName + '_' + pivotKeys.records];
+                    const leafData = PivotUtil.getDirectLeafs(currData, pivotKeys);
                     const hierarchyFields = PivotUtil
-                        .getFieldsHierarchy(currData, [row], PivotDimensionType.Row, pivotKeys);
+                        .getFieldsHierarchy(leafData, [row], PivotDimensionType.Row, pivotKeys);
                     const siblingData = PivotUtil
                         .processHierarchy(hierarchyFields, newData[i] ?? [], pivotKeys, 0);
                     PivotUtil.processSiblingProperties(newData[i], siblingData, pivotKeys);