[IMP] pos_loyalty, point_of_sale: settings integration with new loyalty module

After this commit, the settings of coupons, promotions,
gift cards and loyalty cards are now managed under a
single one field in PoS Settings configuration. Moreover,
this settings field is "global" and shared between the
eCommerce and Sales app.

task-2959620

closes odoo/odoo#99060

Related: odoo/upgrade#3842
Signed-off-by: Masereel Pierre <pim@odoo.com>