Add log streams for all state machines

For debugging state machines, it would be nice to have logs to look back into history, since the Step Functions console is otherwise limited in how far back you can search for past step functions executions. Currently AWS CDK does not add these log groups by default, but it is exposed as an option: https://docs.aws.amazon.com/cdk/api/v1/docs/@aws-cdk_aws-stepfunctions.StateMachine.html#logs