[FIX] sale_coupon: move global coupons to the end of the SO

Steps to reproduce:
 - Install website_sale_coupon
 - Load demo data
 - Create a promotion program that applies on the order
 - Go to the webshop and add 2 different products to the cart

Bug:
The line of promotion is in second place, instead of at the end.

Fix:
move the old sale order line to the end if it applies on all the order

opw-2985632

closes odoo/odoo#102700

Signed-off-by: William Braeckman (wbr) <wbr@odoo.com>