[REF] sale_stock: delivered and procurement quantity

Share the logic for delivered and procurement quantities computation. In
some edge cases, the differences between them triggered an unexpected
behaviour such as showcased in the added tests.

closes odoo/odoo#35257

Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>


Co-authored-by: Arnold Moyaux <arm@odoo.com>