Better error message, fix transaction error recording

[qianl15]

• Found an issue where DBApi error is not properly recorded to the database, thus did not guarantee OAOO behavior. This PR fixes the issue.
• Add a hint error message of InvalidRequestError for transactions, which is often caused by calling commit() and rollback() within a transaction function.
• Improve error message for get_status() within a workflow. If it finds a recorded output but cannot parse workflow status from it, it means the output is corrupted and potentially the workflow is non-deterministic.

Added a bunch of OAOO tests to make sure the behavior is correct.