Improve verification failure reporting UX

Currently, if a verification fails, one gets a message like this:

```
kotlin.AssertionError at /Users/teamcity1/teamcity_work/6326934d18cfe24e/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Throwable.kt:24
```

This does not help to identify the verification that's failed, making it hard to identify what actually fails, especially in flaky test scenarios.