[FIX] mrp: improve mrp BOM report

Steps to reproduce the bug:
- Create a BOM:
    - set the quantity of the finished product and component as more than 1
    - save > print > BOM Structure

Problem:
The report generated shows the qty and cost for production of 1 unit of product, regardless of the BOM quantity

opw-2691632

closes odoo/odoo#80132

X-original-commit: 0700db23
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Djamel Touati (otd) <otd@odoo.com>