[16.0][FIX][purchase_sale_stock_inter_company] multiple products leads to a backorder

[Kev-Roche]

In case of an intercompany purchase > sale with multiple lines / products, the validation of the sale's picking leads to :

• first line / product wil be fill on the purchase picking
• other lines / products will be in a new picking on the purchase side.

This PR add a test and the fix.