[SWT-NNNN] A stable JSON-based ABI for tools integration

[grynspan]

One of the core components of Swift Testing is its ability to interoperate with Xcode 16, VS Code, and other tools. Swift Testing has been fully open-sourced across all platforms supported by Swift, and can be added as a package dependency (or—eventually—linked from the Swift toolchain.)

Because Swift Testing may be used in various forms, and because integration with various tools is critical to its success, we need it to have a stable interface that can be used regardless of how it's been added to a package.

Read the full proposal here.

Checklist:

• [x] Code and documentation should follow the style of the Style Guide.
• [x] If public symbols are renamed or modified, DocC references should be updated.

[grynspan]

@younata This may be of interest to you as a tools author. :)

[grynspan]

@swift-ci please test

[grynspan]

@swift-ci please test