[Export] Hierarchical Grid expanded state is not properly exported when a primaryKey is specified

[mtsvyatkova]

Description

When exporting the Hierarchical Grid to PDF or Excel, the expanded state of rows is not correctly preserved in the exported file.
For PDF exports, only the root-level rows are included in the generated .pdf file, even when child rows are expanded in the UI before export.

• igniteui-angular version:
• browser:

Steps to reproduce

1. Go to the hierarchical-grid.sample.html file and add [primaryKey]="'ID'" to the first grid on the page.
2. Start the demos.
3. Navigate to the 'Hierarchical Grid' sample and expand a row in the first grid.
4. Use the toolbar to export the grid to PDF.
5. Open and inspect the exported file.

Result

Only root-level rows are exported

Expected result

The expanded child rows should also be exported and preserved in the exported file.

Note: Excel exported files contain all rows, but the expanded/collapsed state is not preserved and does not match the state of the grid before export.