Don't match cancellation in NonFatal

[nomisRev]

In Kotlin 1.4 CancellationException was added as a cancellation system for coroutines. We thus shouldn't match CancellationException in NonFatal, or it would be prone to being swallowed in user code.

I.e. if fetchUser is cancelled it throws CancellationException, and in the below snippet it could be easily swalled and mapped to a default error type. This would easily cause bugs, and we should let CancellationException propagate through the program so it can cancel any outer scopes.

val user = Either.catch {
  fetchUser()
}.mapLeft { DomainError.UnkownError(it) }