Introducing: Issue Reporting

[stephencelis]

This PR will bring XCTestDynamicOverlay into a more modern world with a new name, new module, and new APIs.

This library will be a more general set of tools for reporting issues in your code base, and it just so happens to integrate with XCTest and Apple's new Swift Testing framework (in beta).

The basic migration:

// Before:
import XCTestDynamicOverlay
XCTFail("Unexpected code path hit")

// After:
import IssueReporting
reportIssue("Unexpected code path hit")

There's a lot more, but it will be covered when the tools are closer to being ready.