[FIX] pos_loyalty: prevent unwanted free product points correction

Before this commit, purchasing a gift card along with applying a free
product promotion in the same order resulted in the gift card balance
being decreased by the free product price.

Steps to reproduce:
1. Create a buy x get y promo program.
2. Open the POS and use this program and sell a gift card in the same transaction.
3. Activate the promo program and complete the transaction.
The promo program discount will take money of the gift card amount.

Also there is another issue with Loyalty Cards points:
When the reward's product in not valid of the rule, it will decrease
the point when you add the reward.

opw-3284636

closes odoo/odoo#121962

Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>