Support test output.

At the moment, after a test is run if you select the test result from the list, the result panel will say "The test case did not report any output." regardless of if the test contained any `console.log` messages or [`context.diagnostic`](https://nodejs.org/docs/latest-v20.x/api/test.html#contextdiagnosticmessage) messages. It would be great if we could see more output from the tests, particularly by using the `context.diagnostic` method.