Upgrade to version 2 spec

If possible, this test runner should be updated to version 2 of the [test runner interface specification](https://github.com/exercism/docs/blob/main/building/tooling/test-runners/interface.md).

The version 2 spec differs from version 1 in that the `results.json` file contains detailed information on individual tests.
This information includes things like:

- The test status (passing/failing)
- The error message (if failing)
- The test code that was used to run the test

You are completely free on how you want to extract the test code, either via the AST or via finding the test code in the source code text via string manipulation.

Let me know if there are any questions.