Enable optional console output for junit targets

[zilluss]

I want to be able to see the console output for junit targets when using the playground. This would give users more feedback e.g. when implementing coding assignments.

[AlexanderPrendota]

Hello, thanks for the feedback. Yes, I know. The feature has the breaking changes: it becomes incompatible with Kotlin playground client, though I guess it's important for end-users. It has to be supported on the client side first.