[FIX] payment_test: fix token name.

This commit fixes two bugs with payment_test:

First:
Before, payment test would create token without a name.

When you tried to pay your subscription on the portal with these, the following error would occurs:

```
Error to render compiling AST
AttributeError: 'bool' object has no attribute 'replace'
Template: sale_subscription.subscription
Path: /t/t[2]/div/t/t[2]/ul/li[1]/div[3]/t
Node: <t t-esc="account.payment_token_id.short_name"/>

The error occured while rendering the template sale_subscription.subscription and evaluating the following expression: <t t-esc="account.payment_token_id.short_name"/>
```

This commit add a distinct name for these token to avoid errors and confusion.

Secondly,

Before this commit when user tried to make a payment with the payment_test acquirer, the callback method was never called.
This had an impact on module where the callback method is used (mostly subscription).

closes odoo/odoo#60510

Taskid: 2367508
Related: odoo/enterprise#14329
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>