Merged PR 4425: Reworks Billable Bookings metrics

# Description

Changes:
* On Est. Billable Bookings, keeps previous logic for Old Dash while assuming the first billable service for New Dash
* Adds a Billable Check Out Bookings in Check Out bookings, as defined in the requirements.

# 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: #27619

models/reporting/general/monthly_aggregated_metrics_history_by_deal.sql

@@ -19,6 +19,7 @@ select
     check_out_bookings as check_out_bookings,
     cancelled_check_out_bookings as cancelled_check_out_bookings,
     not_cancelled_check_out_bookings as not_cancelled_check_out_bookings,
+    billable_check_out_bookings as billable_check_out_bookings,
     cancelled_check_out_bookings_rate as cancelled_check_out_bookings_rate,
     billable_bookings as billable_bookings,
     created_guest_journeys as created_guest_journeys,