[FIX] loyalty: prevent product id overwriting

**Current behavior:**
Creating a promo type loyalty program and editing the
'products' field in the 'Among' section of the rule created by
default at the bottom of the form view before saving the
program will cause the products selected in this field to be
cleared upon saving the program.

**Expected behavior:**
Filling out this field of the default rule before saving the
overarching loyalty program should result in the same behavior
as doing so after saving the program. That is, the field should
save the user's input.

**Steps to reproduce:**
1. Create a new loyalty program in the Discount & Loyalty tab

2. Give it a name and, before saving the program, edit the
     'Products' field of the default rule that is created at
     the bottom of the form to have at least one value

3. Now save the program and observe that the 'Products' field
     has been cleared of the previously selected values

**Cause of the issue:**
In the form view for the loyalty.program there are two
instances of the field trigger_product_ids which are set to be
invisible unless creating a specific program type. This field
is set to be related to rule_ids.product_ids in its definition
within the loyalty.program class definition. Thus, when the
user saves the program and rule concurrently, the empty
trigger_product_ids field overwrites the product_ids field
and whatever the user had populated it with is cleared.

The reason it only happens to the default rule and not ones
which are manually added before saving the program is because
in the traverse_related() method in fields.py, only the first
record of the related field is returned to be modified. In this
case, it means only the first rule's product_ids field is
overwritten.

**Fix:**
Overwrite the create() method in program.loyalty and check if
the program being created is of type 'gift_card' or 'ewallet'
then, if so, delete the trigger_product_ids key,val from the
dictionary so it will not later override the products specified
in the loyalty rule.

opw-3669953

closes odoo/odoo#155093

X-original-commit: 7ed0a773b6e0711b127f236ce665c35202d973bc
Signed-off-by: Vincent Ethan <etvi@odoo.com>

addons/loyalty/models/loyalty_program.py

@@ -598,3 +598,15 @@ class LoyaltyProgram(models.Model):
                 })]
             },
         }
+
+    @api.model_create_multi
+    def create(self, vals_list):
+        """
+        trigger_product_ids will overwrite product ids defined in a loyalty rule in certain instances. Thus, it should
+        be explicitly removed from an incoming vals dict unless, of course, it was actually a visible field.
+        """
+        for vals in vals_list:
+            if 'trigger_product_ids' in vals and vals['program_type'] not in ['gift_card', 'ewallet']:
+                del vals['trigger_product_ids']
+
+        return super().create(vals_list)