[FIX] account, stock_account: invoice in multi-currency

- Activate Anglo-Saxon accounting
- Set a foreign currency rate to 2.0
- Create a product A:
  Inventory Valuation: 'Automated'
  Costing Method: 'Standard Price'
  Cost: 10.0
  Public Price: 100.0
- Create an invoice in foreign currency
- Add 1 unit of A => the total amount is 200.0
- Confirm the invoice

The Amount Due is 100.0 instead of 200.0.

This happens because the Anglo-Saxon lines have the company currency,
while the other lines have the foreign currency. Because of this, the
`_compute_amount` method considers the move as multi-currency to compute
the various amount. However, the Anglo-Saxon lines should be neglected.

This happens from 14.0 because all lines have a currency. In previous
versions, lines in the company currency didn't have the `currency_id`
set.

opw-2390107

closes odoo/odoo#62543

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>