Merged PR 2689: KPIs by Billing Country

# Description

Adds Billing Country dimension in KPIs, but does not expose them to reporting yet.
Silly thing, based on the macros I built, I cannot make incremental changes unless changing all models. This will need to be adapted, happy to hear your thoughts on how we do it.
Additionally, I have lack of performance of the model `mtd_guest_payments_metrics`. It takes around 5 min to execute, but technically the end-to-end runs in one shoot without breaking.
It's a complex PR because it changes many files, but you will see that:
* It mostly changes the join conditions for the dimensions or the schema tests,
* I tried to be very careful and add things step-by-step in the commits.

Goal is NOT to complete the PR yet until we see how we can improve performance. I can say though that data end-to-end looks ok to me, but would benefit from checking with production data for the new dimension

Update 30th Aug
* Added a new commit that includes `id_user_host` in `int_core__verification_payments`. Happy to discuss if it makes sense or not. But it changes the execution from ~600 sec to ~6 sec because it avoids a massive repeated join with `verification_requests`.

# Checklist

- [X] The edited models and dependants run properly with production data.
- [X] The edited models are sufficiently documented.
- [X] The edited models contain PK tests, and I've ran and passed them.
- [X] I have checked for DRY opportunities with other models and docs.
- [ ] I've picked the right materialization for the affected models. **To check because of performance issues**

# Other

- [ ] Check if a full-refresh is required after this PR is merged.

Related work items: #19082

macros/business_kpis_configuration.sql

@@ -9,7 +9,8 @@ Please note that strings should be encoded with " ' your_value_here ' ",
 {% macro get_kpi_dimensions() %}
     {% set dimensions = [
         {"dimension": "'global'", "dimension_value": "'global'"},
-        {"dimension": "'by_number_of_listings'", "dimension_value": "active_accommodations_per_deal_segmentation"}
+        {"dimension": "'by_number_of_listings'", "dimension_value": "active_accommodations_per_deal_segmentation"},
+        {"dimension": "'by_billing_country'", "dimension_value": "billing_country_iso_3"}
     ] %}
     {{ return(dimensions) }}
 {% endmacro %}