SAGA Loop循环事务补偿入参问题咨询

### Ⅰ. Issue Description
SAGA Loop循环事务补偿入参问题咨询。

### Ⅱ. Describe what happened
使用SAGA Loop循环事务时，当事务发生补偿，循环事务里的单个子事务补偿方法入参无法获取到集合单个元素及集合下标。
试了test用例中的org.apache.seata.saga.engine.db.StateMachineDBTests.testSimpleStateMachineWithLoopCompensate()方法，似乎也无法获取到。
请问需要如何配置才能在Loop子事务补偿时入参获取到集合单个元素信息。

### Ⅵ. Environment:

- JDK version(e.g. `java -version`):8
- Seata client/server version: 2.0.0

Start with org.apache.seata.saga.engine.db.StateMachineDBTests.testSimpleStateMachineWithLoopCompensate() using JDK 8 and Seata 2.0.0. Trace how the Loop child compensation receives arguments and whether the collection element and index are propagated. Done means establishing the required configuration or confirming the behavior as a defect with a reproducible test.

Written by the indexing model from the issue text.