Don't replay autocommit statements with transaction_replay

Problem Description

The transaction_replay safe mode described in MXS-4712 also includes a smaller subtask that will have big impact in practice: preventing the replay of statements that are done with autocommit enabled and that are outside of an explicit transaction. This will make the behavior of transaction_replay much easier to use in situations where there is a mix of autocommit statements and transactions that modify the database.

Implementation

Make it so that transaction_replay_safe_commit=true (the default) disables retrying of queries outside of transactions when transaction_replay=true and transaction_replay_safe_commit=true is being used.