[FIX]Invoice created from purchase order with invoicing method : Based on Receptions, doesn't consider purchase order pricelist currency

Fixed the bug with invoicing purchase order.

Steps to reproduce:

    Company currency is EUR
    Create new purchase price list in CZK (Product_1 price is 1000CZK)
    Set Purchase setting Default invoicing control method to “Based on receptions”
    Create and confirm new purchase order with new price list
    Go to related Incoming shipment and receive products.
    Confirm invoice creation.

Current behavior:

    Open newly created invoice. Prouct_1 unit price is 37.65. Total is 37.65 CZK instead of 1000 CZK.

Expected behavior:

    Prouct_1 unit price is 1000. Total is 1000 CZK.
This means doing 2 conversions: eur -> czk -> eur and losing precision
Instead you can use `move_line.purchase_line_id.price_unit`