build(repo): structure the repo into postgresql subdirectory with separate template and internal tests

postgresql/template/partitions.get_all.sql

@@ -0,0 +1,6 @@
+SELECT 
+    table_name,
+    future_partitions,
+    total_size_bytes,
+    EXTRACT(EPOCH FROM (now() - last_updated)) AS age_seconds
+FROM partitions.monitoring;