[PY-398] Polling on Item Push

[saurbhc]

Problem

1. Before pushing an item to the next stage, we need a way to make sure those items should have complted the processing.
2. dataset-stage might not be the 1st staged returned from the API, which raises an error when pushed to next stage.

Solution

1. Add Pooling on Item Push (before pushing item to next stage), with an optional wait parameter
2. Additionally, fix dataset stage logic in Workflow obj

Changelog

Pooling on Item Push + Fix dataset stage logic

[linear]

PY-398 Polling on Item Push

Darwin py v2 workflow upload currently pushes new items to the next stage automatically but doesn't check whether processing of the item is complete.

• poll each item on stage, waiting for complete
• once all complete, then push to stage
• Add status check to all remaining stage item move code
  • potentially with flag for behaviour, wait=True to poll, but if False Raises Exception

[owencjones]

I like it, with some suggestions - review comments before merge

[Nathanjp91]

Minor changes on where the sleep happens.

[Nathanjp91]

I'm happy now with the changes.