[FIX] point_of_sale: Load all existing Payment Method but displayed linked ones

Before, when using the manage order, if a payment method was used and then removed from the pos.config,
we couldn't load the old order anymore because of unknow reference.
To fix this, we load all methods at the opening of the pos but when we display the payment methods we only show those in the pos.config.

closes odoo/odoo#71263

Task-id: 2541708
Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>