Add new start-up tasks

[gabegma]

Description:

On big datasets, the behavioral testing summary and class overlap modules would error out in the UI, while they were being computed. I added them both to the start-up, and that forced me to refactor so we could define what dataset splits to send to a particular start-up task.

Checklist:

You should check all boxes before the PR is ready. If a box does not apply, check it to acknowledge it.

• ISSUE NUMBER. You linked the issue number (Ex: Resolve #XXX).
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• DEV CHANGES.
  • Update the documentation if this PR changes how to develop/launch on the app.
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  • Add unit tests, docstrings, typing and comments for complex sections.

[gabegma]

I'm waiting on the changes in #350, about including datasets in the hash before removing this from draft.

[JosephMarinier]

I suspect we will end up not using those lines, but just in case, some small details...

[JosephMarinier]

Good job! And thank you, I learned a bunch of things. 👍