[test] Ensure stable object id in test checkpoint data builder (#20839)

## Description 

This will be useful when we need to query data from the DB and sort by
object ID.

## Test plan 

CI

---

## Release notes

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- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:

crates/sui-types/src/test_checkpoint_data_builder.rs

@@ -489,8 +489,12 @@ impl TestCheckpointDataBuilder {
     }
 
     /// Derive an object ID from an index. This is used to conveniently represent an object's ID.
+    /// We ensure that the bytes of object IDs have a stable order that is the same as object_idx.
     pub fn derive_object_id(object_idx: u64) -> ObjectID {
-        ObjectID::derive_id(TransactionDigest::ZERO, object_idx)
+        // We achieve this by setting the first 8 bytes of the object ID to the object_idx.
+        let mut bytes = [0; ObjectID::LENGTH];
+        bytes[0..8].copy_from_slice(&object_idx.to_le_bytes());
+        ObjectID::from_bytes(bytes).unwrap()
     }
 
     /// Derive an address from an index.