[FIX] sale_mrp, sale_stock: compute is_reverse based on move type

Very similar to the usecase in commit dafe732e6874fbdd15dfd213b5c5c0cde93e534e

Steps to reproduce:

- Install Accounting, Sales, Stock
- Create a product category PC:
	- Costing method: FIFO
	- Inventory Valuation: Automated
- Create a product P:
    - Type: Storable
    - Product Category: PC
- Create a Sales Order SO with 1 x P at cost 10
- Confirm delivery
- SO > Create Invoice > Post
- SO > Return the delivery
- Change product price from 10 to 6
- SO > Create Invoice (!!)
- The invoice will be marked as a credit note automatically
- Post the invoice

Issue:

The product is listed in the journal items, which is correct,
but its value is 6 while it should be 10.

If we create the invoice from the Sales Order instead of adding a
credit note, then the move lines will not be considered reversed,
since they do not have an associated invoice.

Solution:

Consider the move type when deciding if the move line is reversed or not.

opw-3077772

closes odoo/odoo#111035

Signed-off-by: Adrien Widart <awt@odoo.com>