[Pitch] Add Issue Capturing & Test-Utility-specific module to Swift Testing

Hello everyone, The Swift Testing Workgroup has been discussing this as a pre-pitch for ~1.5 months now. This one grew out of the pitch for polling confirmations, and I feel it's past time to bring it to a wider audience. You can read the pitch as a rendered document on GitHub here. It is also pasted down below. This has a working implementation! Try it out by following these steps: Add my fork of Swift Testing as a dependency, specifying the rbrindle/issue-responder-chain branch: dependenc...