S3ToStepFunctions: add a SQS FIFO Queue to get exactly-once delivery

In using this construct I found I was spending a lot more than expected because I was getting many duplicate events, and running my ML step function is quite expensive. I suggest adding a FIFO queue to get exactly-once delivery semantics (or change to an S3-SNS-SQS-Stepfunction workflow).

This is a :rocket: Feature Request

Start at the S3ToStepFunctions construct and inspect its current event-delivery path. Compare the proposed SQS FIFO option with the alternative S3-SNS-SQS-StepFunctions workflow, then define which approach provides the requested delivery semantics and what behavior should demonstrate completion.

Written by the indexing model from the issue text.