Investigate if we can make a generic LSP test reporter that uses JSON to format the output. If not, then just implement one for Minitest and Test Unit

[vinistock]

When running multiple tests as part of a single command, associating which output belongs to which test becomes challenging if all they're doing is printing unstructured messages to stdout.

We need to be able to report test runs using structure outputs, like JSON, so that we can know:

• When a test started running
• If a test was skipped, succeeded, failed or errored
• When a test printed output

And we need to have a way to associate this information to the test item it belongs to.

Investigate if we can provide a generic JSON reporter to be used with all test frameworks. If there are substantial differences and we can't account for all frameworks, then implement the one for Minitest and Test Unit and try to see if there are bits that can be shared for add-ons.