fix(core-flows): Add missing cart sales channel id fields to be part of the application context (#10142)

RESOLVES SUP-185

**What**
The cart fields to be fetched for the promotion workflow was not including the sales_channel_id, making any rules being constraint to that fields not being validated against this property.

packages/core/core-flows/src/cart/utils/fields.ts

@@ -9,6 +9,7 @@ export const cartFieldsForRefreshSteps = [
   "currency_code",
   "metadata",
   "completed_at",
+  "sales_channel_id",
   "region.*",
   "items.*",
   "items.product.id",