graphql-alt: indices for packages and epochs

## Description

Augment indices to make the following query patterns efficient:

- Latest epoch for a given checkpoint
- Latest package for a given checkpoint
- Latest package below a given version
- Paginate package versions

## Test plan

Take local copies of the relevant tables, without indices and EXPLAIN
the relevant queries. Then add the indices and re-EXPLAIN the queries to
confirm that they had the desired effect.

Author: amnn

crates/sui-indexer-alt-schema/migrations/2025-04-29-144444_kv_packages_indices/down.sql

@@ -0,0 +1,8 @@
+DROP INDEX IF EXISTS kv_packages_id_cp_version;
+
+CREATE INDEX IF NOT EXISTS kv_packages_id_version_cp
+ON kv_packages (original_id, package_version, cp_sequence_number);
+
+CREATE INDEX IF NOT EXISTS kv_packages_system_packages
+ON kv_packages (cp_sequence_number, original_id, package_version)
+WHERE is_system_package = true;

crates/sui-indexer-alt-schema/migrations/2025-04-29-144444_kv_packages_indices/up.sql

@@ -0,0 +1,10 @@
+DROP INDEX IF EXISTS
+    kv_packages_id_version_cp,
+    kv_packages_system_packages;
+
+CREATE INDEX IF NOT EXISTS kv_packages_id_cp_version
+ON kv_packages (original_id, cp_sequence_number DESC, package_version DESC);
+
+CREATE INDEX kv_packages_system_packages
+ON kv_packages (original_id, cp_sequence_number DESC, package_version DESC)
+WHERE is_system_package = true;

crates/sui-indexer-alt-schema/migrations/2025-04-29-151618_kv_epoch_start_indices/down.sql

@@ -0,0 +1 @@
+DROP INDEX IF EXISTS kv_epoch_starts_cp_lo;

crates/sui-indexer-alt-schema/migrations/2025-04-29-151618_kv_epoch_start_indices/up.sql

@@ -0,0 +1,2 @@
+CREATE INDEX IF NOT EXISTS kv_epoch_starts_cp_lo
+ON kv_epoch_starts (cp_lo);