optimizing reporting_patient_states partitioned refresh (#5700)

**Story card:**
[sc-16750](https://app.shortcut.com/simpledotorg/story/16750/make-partitioned-refresh-performant)

## Because

In India partitioned refresh was running for 2 weeks, which is not
acceptable.

## This addresses

Adding a month_date index on reporting_prescriptions to make the join,
which provides "titrated" column, faster.
Using an indexed field, month_date, for joins in
reporting_patient_blood_sugars, reporting_patient_blood_pressures and
reporting_patient_visits to improve the overall performance.

## Test instructions

Run `rake "db:refresh_reporting_views"`
For small dataset, this optimization is not measurable. 
We tested this in India prod, after these optimizations, refresh was
completed in 15 mins.

---------

Co-authored-by: Ayushi Agrawal <[email protected]>

Author: aagrawalrtsl

db/migrate/20250924101441_add_month_date_index_reporting_prescriptions.rb

@@ -0,0 +1,13 @@
+class AddMonthDateIndexReportingPrescriptions < ActiveRecord::Migration[6.1]
+  self.disable_ddl_transaction = true
+
+  def up
+    add_index :reporting_prescriptions, [:month_date],
+      name: "reporting_prescriptions_month_date", algorithm: :concurrently
+  end
+
+  def down
+    remove_index :reporting_prescriptions,
+      name: "reporting_prescriptions_month_date"
+  end
+end