We are going to deprecate `WITH_RUNTIME` directive. The main reason
behind this change is that `WITH_STDLIB` directive better describes
its meaning, specifically it will add kotlin stdlib to test's classpath.
* The members of Result are isSuccess, isFailure, exceptionOrNull, getOrNull
* The rest of API is implemented via inline-only extensions
* There are two internal functions to hide detailed mechanics of an internal
Result.Failure class: createFailure and throwOnFailure
* Result.toString is explicit: either Success(v) or Failure(x)
See KT-26538