feat: rust core API dev branch

[aaronc]

Description

This is the dev branch for the rust core API. It will probably be in draft for a while and serve as a long-term feature branch while we do internal testing.

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Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title, you can find examples of the prefixes below:
• confirmed ! in the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• reviewed "Files changed" and left comments if necessary
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• updated the relevant documentation or specification, including comments for documenting Go code
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

Please see Pull Request Reviewer section in the contributing guide for more information on how to review a pull request.

I have...

• confirmed the correct type prefix in the PR title
• confirmed all author checklist items have been addressed
• reviewed state machine logic, API design and naming, documentation is accurate, tests and test coverage