[FIX] purchase: orderpoint on existing PO
[FIX] purchase: orderpoint on existing PO

- Create product A:
Reordering rule of 5 units
Set a vendor V
- Create a SO with 1 unit of A
- Create a PO with 1 unit of A for vendor V
- Run the scheduler => the PO contains 6 units
- Run the scheduler => the PO contains 12 units

The PO should not be updated the second time the scheduler is run.

It occurs because the `orderpoint_id` is not set on the PO line, while
the `_quantity_in_progress` method searches for PO lines with the
orderpoint set.

opw-2000962

closes odoo/odoo#33798

Signed-off-by: Nicolas Martinelli (nim) <771435c469f83f6aa9c405ac5e1ed06314a94f2d@odoo.com>
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo