Support multi-statement transactions in YAML

[hatyo]

Currently, all YAML tests run in auto committed mode, we would like to add support to running tests in non-auto-committed transaction to get more test coverage for a certain type of workflows that do multi-statement transactions.

[hatyo]

Thanks @ScottDugas for the reminder, the server does not support multi-statement transaction. i.e. this is only supported in embedded mode at the moment.

[ScottDugas]

Some thought would have to also be put into how we want to handle multi-server tests, since you want the entire transaction to run against one connection.