Add test for SAVEPOINT with Foreign Key function

[YangKeao]

Enhancement

We need to test the following cases:

1. Begin-> Savepoint -> Insert parent record -> Insert child record to reference the parent record -> Rollback -> We cannot insert the child record.
2. Begin -> Insert parent record -> Savepoint -> Insert child record -> Rollback -> We can remove the parent record now in this transaction.
3. Insert parent record -> Begin -> Savepoint -> Insert child record -> Rollback to Savepoint. We cannot update/remove the parent record in another transaction, because the lock will be released after commit.