fix: Ensure drill-through chart field works consistently across CRUD and Explore paths

Fixes two issues with the drill-through chart configuration:

1. **SelectAsyncControl crash on clear**: Fixed isLabeledValue function to handle null values properly when clearing selections
2. **Missing field in Explore path**: Added drill_through_chart_id to both dataset API response and SqlaTable.data property serialization

This ensures the drill-through chart field loads and saves correctly whether accessed from:
- Datasets CRUD interface
- Explore → Edit Dataset flow

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

superset-frontend/src/explore/components/controls/SelectAsyncControl/SelectAsyncControl.test.tsx

@@ -104,3 +104,15 @@ test('Should send correct props to Select component - function onChange multi:fa
   userEvent.click(await screen.findByText('onChange'));
   expect(props.onChange).toHaveBeenCalledTimes(1);
 });
+
+test('Should handle null value without crashing when clearing selection', () => {
+  const props = createProps();
+  const { rerender } = render(<SelectAsyncControl {...props} />, {
+    useRedux: true,
+  });
+
+  // Simulate clearing the selection by passing null value
+  expect(() => {
+    rerender(<SelectAsyncControl {...props} value={null} />);
+  }).not.toThrow();
+});