JS support for Kotest runner

JS seems like the easiest next step, but PRs for native platforms are welcome too!

- [ ] in `selfie-lib`, move tests from `jvmTest` to `commonTest` one by one and implement the missing part
- most tests are already in `commonTest`, here is a suggested order for the 5 which are stuck in `jvmTest`
- [ ] `LineReaderTest`, `SnapshotValueReaderTest`, `SnapshotReaderTest`, `SnapshotFileTest` (sequentially in one PR)
- [ ] `RecordCallTest` in its own PR, perhaps needs to stay platform-specific
- [ ] in `selfie-runner-kotest` search for `TODO: https://github.com/diffplug/selfie/issues/186`
- [ ] move `HarnessVerifyTest` out of `jvmTest` and into `commonTest`

Inizia in `selfie-lib` esaminando i cinque test elencati in `jvmTest` e i loro corrispondenti già presenti in `commonTest`, quindi cerca `TODO: https://github.com/diffplug/selfie/issues/186` in `selfie-runner-kotest`. Sposta e implementa i test in sequenza quando possibile, mantenendo `RecordCallTest` specifico per la piattaforma se necessario, e sposta `HarnessVerifyTest` in `commonTest`; il lavoro è completato quando il runner JS supporta questi test.

Scritto dal modello di indicizzazione a partire dal testo della issue.