This commit fixes a bug (corner case) concerning payments to yourself where an early payment discount is applied.

**Details / steps to reproduce the bug:**
1. Create an invoice
2. Select your own (currently selected) company as customer
3. Select some payment term with early payment discount (e.g. '2/7 Net 30')
4. Confirm the invoice.
5. Click "Register Payment" and keep the default values (i.e. "Mark as fully paid" should be selected)
6. Click "Create Payment"
7. A User Error like the following should appear (with different journal entry names):
   "Journal Entry Draft Entry PBNK1/2023/00001 (INV/2023/00005) is not valid. In order to proceed, the journal items must include one and only one receivable/payable account (with an exception of internal transfers)."


**Why the bug happens:**
The early payment discount adds some extra lines to the journal entry associated with the payment.
Currently those extra lines are classified as "counterpart lines" since the customer is our own company.
But there must be exactly 1 "counterpart line".

**How the bug is fixed:**
The condition that classifies the extra lines as "counterpart lines" was only intended for internal transfers.
Each company has a related "transfer account" that is used as an intermediary account for internal transfers.
Thus the old condition (c.f. commit diff) when checking whether a line is a "counterpart line"
can be replaced by checking whether the account associated with the line is the "transfer account" of our company.


task-3388294

Forward-Port-Of: odoo/odoo#127412

Steps to reproduce:

1. Install partner_commission, stock
2. Create two commission plans
	- 1. Name = 10, Rules: Product Category = All, Rate = 20
	- 2. Name = 20, Rules: Product Category = All, Rate = 20
3. Create product P
	- Product Type = Storable, Sales Price = 100
	- Sales Tab: Invoicing Policy = Ordered Quantity
4. Create or modify a contact C
	- Partner Assignment: Commission Plan = 10
5. Create sales order
	- Customer = any, Referrer = C, Commission Plan: 20
	- Order Lines: Product = P, Quantity = 1
	- Confirm sales order, Create and view invoice
	- Confirm invoice, Register full payment
6. Go to Purchase, see the RfQ generated for the sales order

Issue:

The commission price on the RfQ is 10, instead of the expected 20. This happens because when we create the RfQ, we only consider the commission plan of the referrer, but not the commission plan specified on the sales order.

Solution:

Consider the commission plan on the sales order when creating the RfQ.

opw-3217890

Forward-Port-Of: odoo/enterprise#43784
Forward-Port-Of: odoo/enterprise#42770