[FIX] sale_{stock,mrp}: repost inv with cogs

To reproduce the issue:
(Also need: account_accountant,purchase)
1. Setup a product P
   - Storable
   - Category:
     - FIFO + Auto
2. Process a PO with 1 x P at $10
3. Process a PO with 1 x P at $50
4. Create and confirm a SO with 1 x P
    - Because of FIFO, the value of the delivered product is $10
5. Process the delivery
6. Post the invoice
7. Add credit note
   - Credit Method: Full refund and new draft invoice
8. Post the second invoice

Error: The cogs are based on the second received product ($50), they
should rather be based on the delivered one

When computing the anglo-saxon unit price of the product, we consume
the outgoing SVLs, and we consider the already-invoiced quantity.
Here is the issue: we pretend that this quantity is 1, because of
the first invoice, but this should be balanced with the quantity of
the credit note

OPW-3109789

closes odoo/odoo#114346

X-original-commit: d8e286ad
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Adrien Widart <awt@odoo.com>