Add iorNel builder and Ior.toIorNel function

[sampengilly]

No description provided.

[sampengilly]

Unfortunately we can't easily have something like a .bindNel() extension function on an Ior inside an iorNel block without either duplicating IorRaise (or opening it for extension). Context receivers could help here going forward. For the initial submission I've kept it simple with an additional converter function to convert an Ior to an IorNel before binding normally

[sampengilly]

It will probably be necessary to build a new IorNelRaise<Error> type I think. If we want to be able to bind individual Error items within the raise block for a nicer API:

fun someEitherFunc() = Throwable().left()

iorNel<Throwable, Nothing> {
    someEitherFunc().bind()
    // vs
    someEitherFunc().mapLeft { it.nel() }.bind()
}

[serras]

@sampengilly could you please run ./gradlew apiDump on this branch and commit the results? The automatic .api updater doesn't seem to work in forks :/