[Pitch] Attachments in the Swift Testing JSON event stream

Attachments are a popular feature of Swift Testing (and XCTest on Apple's platforms). When a test saves an attachment, it should be recoverable later by whatever tool(s) is used to analyze the test run. This is easy enough in Xcode or when using the Swift VS Code plugin, but we're starting to add support for Embedded Swift, where there might not even be a file system where attachments can be saved in the first place. Swift Testing in Embedded Swift will rely on the JSON event stream to feed inf...