[FIX] - sale_commission: Fixed module to correctly calculate commissions.

Changes
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* [FIX] - Modified the total sales calculation to used the amount discounted instead of the total amount.
* [FIX] - sale_commission: Modified credit calculation and estimated the correponding credit excluding taxes.
* [FIX] - sale_commission: Modified wrong field name in credit calculation.
* [IMP] - sale_commission: Commissions now manage the state of the related payment.
* [IMP] - sale_commission: Updated translation and added domain to filter payments.