[FIX] purchase : Account analytic default changed by user is reset in invoice

Reproduce :
1. Add a default analytical rule: if Coin Gourmand partner then Administrative analytical account
2. Create a PO at the Coin Gourmand supplier, add a product, and select the Internal analytical account.
3. Bill for this product.

Result :
Internal analytical account has disappeared from the invoice line. It has been replaced by Administrative.

Issue :
AccountMove.create() computes an account in the move and this causes the analytic account to be reset at its default value from the rule.

Fix :
Since the account pocalypse in 13.0, account.move is making magic things during the creation of the invoice to create dynamically the invoice lines like account.invoice did before this huge refactoring.
The create is making a 'New' record to simulate the onchange but this code is a hack triggering unexpected recomputation like the analytic account.
To avoid that, we ensure to assign the minimum number of fields to preserve fields like the analytic account.

closes odoo/odoo#76751

Signed-off-by: Laurent Smet <smetl@users.noreply.github.com>