Steps to reproduce:
- In User settings add 'allocation reports' group to the admin User
- In Inventory settings enable allocation reports
- Create a stored product with 0/0 reordering rules and set a vendor
- Create an SO for that product
- Confirm the generated PO and click assign all on its receipt's allocation report
- Reduce the quantity on the SO and save

Bug:
a return is created instead of adjusting the quantity to deliver
the stock moves were not merged because their procurement method do not
match ('make_to_stock' / 'make_to_order')

Fix:
ignore procurement method when merging the moves
(introducing new config parameter)

opw-3621316

closes odoo/odoo#154658

X-original-commit: 54bd4416
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Walid Hanniche (waha) <waha@odoo.com>