Support test output.

[zeel01]

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 messages. It would be great if we could see more output from the tests, particularly by using the context.diagnostic method.

[connor4312]

This is an issue with the Node.js test runner in that it always reports console logs asynchronously so we cannot very well correlate logs to specific test cases. But we could just natively dump them into the main test output like other CLI reporters often do