Description of the issue/feature this PR addresses

When printing a sale order from the POS Sale Order Management screen, the
SelectionPopup ("What do you want to print?") is always displayed whenever at
least one print report is configured in the POS settings
(print_sales_order_ids), including the degenerate case of a single configured

This forces the cashier to perform a redundant click to select the only
available option on every print, which slows down checkout and is error-prone
in high-volume stores.

Current behavior before PR

In SaleOrderManagementScreen._printSaleOrder, the popup is shown whenever
print_sales_order_ids.length > 0. With a single configured report the cashier
still has to open the popup and pick the only item in the list before the report
is generated.

Desired behavior after PR is merged

• Exactly one report configured: the popup is skipped and the report is
  executed directly via do_action, reusing the existing error handling.
• More than one report configured: behavior is unchanged — the selection
  popup is shown so the cashier can choose.
• No report configured: behavior is unchanged — the existing error popup is
  shown.

How to reproduce (runboat)

1. Install pos_sale_order_print.
2. In POS settings, configure a single report in "Print sale orders".
3. Open a POS session, go to the Sale Order Management screen, select an order
   and print it.
4. Before: a selection popup appears with a single option.
   After: the report is generated directly, with no popup.
5. Configure two or more reports and repeat: the selection popup is still
   shown.

FL-556-7059