This commit makes it so when the bom structure report (Structure & Cost
smartbutton) is opened the product quantity defaults to the BoM's
`product_qty` amount rather than 1.

Steps to reproduce:
- Create/open a BoM
- Set `product_qty` to any value greater than 1
- Click on "Structure & Cost" button.

Expected result: product quantities scaled to the `product_qty`
Actual result: product quantities scaled to Quantity = 1

closes odoo/odoo#65732

Task: 2429885
X-original-commit: 30c05ad9
Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>