[ideas] Set storage = "worker" and retrieval = "worker" by default

[wlandau]

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Description

In highly parallel workloads, I almost always recommend storage = "worker" and retrieval = "worker" so that the parallel workers manage the data instead of putting the burden on the main process. The default values for both are "main" only because I envisioned cloud-based workloads where data may need to travel over the network. In practice, cloud pipelines almost always have some kind of object storage (or database storage) such as an S3 bucket. So I think I should set "worker" as the default for both. But first, I would just like to check with those of you who follow the discussions to see if this would have any unintended consequences.

[wlandau]

Done as of 27c9b0f