Add support for detecting tests in source files, and implement it for Rust (#11195)

Continuing work from #10873 

Release Notes:

- N/A

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Co-authored-by: Mikayla <mikayla@zed.dev>
5a71d8c7f1Piotr Osiewicz committed on 5/5/2024, 2:32:48 PM· committed by GitHubparent14c7782
29 files changedLine totals unavailable