First rewrite of data-executor APIs and structure...

[ndubois-legion]

Summary

Design the crates, the basic APIs and data structures for the data-executor, for both the client-side & server. Also think of the local scenario, where we could have locally a daemon-like running the data-executor/data-compiler/compilers, for better reactivity. Don't forget the Amazon SQS server-side in the design.

https://aws.amazon.com/sqs/faqs/