Return location of test in json report

[razzeee]

It would be helpful to get the location of a test. At least the line number, column would be a bonus.
I'm not too sure if we need the file path too. But it might not hurt?

Similar to: rtfeldman/node-test-runner#368

[mpizenberg]

Also related to that issue is the usage of labels to match tests results and tests detection inside VSCode client plugin. I need to have a look at that (this is a reminder comment for me).

• https://github.com/elm-tooling/elm-language-client-vscode/blob/fea3ef02239b35608e63858d636b8263c453282b/client/src/test-runner/util.ts#L87
• https://github.com/elm-tooling/elm-language-client-vscode/blob/fea3ef02239b35608e63858d636b8263c453282b/client/src/test-runner/runTestSuite.ts#L55

[razzeee]

Yes, I would also think this makes more sense in tandem.

Maybe we should even check the new vscode api and see if there's something obvious, that's missing https://github.com/microsoft/vscode/blob/main/src/vs/vscode.d.ts#L14406
https://code.visualstudio.com/api/extension-guides/testing