Add the LogManagerAccessor interface

The PartitionManager will close a partition when it becomes idle. As a result, it is possible for a LogManager before its LogConsumer is able to acknowledge a completed transaction.

To ensure that the LogManager is active for acknowledgement, add a new LogManagerAccessor interface that exposes the CallLogManager function. This will start the TransactionManager for the requested partition, if necessary, and then execute the provided function against the manager.