Merged PR 2522: Don't Repeat Yourself for KPIs - Applied to Bookings

# Description

What's new:
- Creation of `get_kpi_dimensions`: new macro to have a single point of source of configuration for dimensions for the KPIs. It's a way to enforce global variables on-demand. I kind of like this approach and we could do it for Xero models as well :)
- Modification of `int_core__mtd_booking_metrics` and `int_dates_mtd_by_dimension`: removal of duplicated code within the dimension context. Uses Jinja code and applies different configurations depending on the dimension chosen. Still, different metrics are placed in different CTEs. I believe it might be possible to also configure metrics BUT at the cost of over-complexifying the macro logic, so I wouldn't go for it at this stage.

# 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.**
- [X] I've picked the right materialization for the affected models.

# Other

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

Related work items: #19325

macros/get_kpi_dimensions.sql

@@ -0,0 +1,13 @@
+/*
+Provides a general configuration for the Dimensions available for the KPIs.
+Please note that strings should be encoded with " ' your_value_here ' ",
+    while fields from tables should be specified like " your_field_here "
+*/
+
+{% macro get_kpi_dimensions() %}
+    {% set dimensions = [
+        {"dimension": "'global'", "dimension_value": "'global'"},
+        {"dimension": "'by_number_of_listings'", "dimension_value": "active_accommodations_per_deal_segmentation"}
+    ] %}
+    {{ return(dimensions) }}
+{% endmacro %}