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

models/intermediate/core/schema.yaml

@@ -542,6 +542,7 @@ models:
                 values:
                 - global
                 - by_number_of_listings
+                - by_billing_country
       
       - name: dimension_value
         data_type: string
@@ -577,6 +578,7 @@ models:
                 values:
                 - global
                 - by_number_of_listings
+                - by_billing_country
       
       - name: dimension_value
         data_type: string
@@ -612,6 +614,7 @@ models:
                 values:
                 - global
                 - by_number_of_listings
+                - by_billing_country
       
       - name: dimension_value
         data_type: string
@@ -647,6 +650,7 @@ models:
                 values:
                 - global
                 - by_number_of_listings
+                - by_billing_country
       
       - name: dimension_value
         data_type: string
@@ -682,6 +686,7 @@ models:
                 values:
                 - global
                 - by_number_of_listings
+                - by_billing_country
       
       - name: dimension_value
         data_type: string
@@ -870,6 +875,13 @@ models:
         data_type: date
       - name: refund_payment_reference
         data_type: character varying
+      - name: id_user_host
+        data_type: character varying
+        description: |
+          UUID of the Host linked to the Verification Request
+          that has a payment. It's included here to speed up
+          KPIs execution, even though the host itself has nothing 
+          to do with the guest payments.
       - name: id_guest_user
         data_type: character varying
       - name: id_verification