smithy4s-cats: provide transformers for EitherT

Now that we have a Cats module, we should provide a generic (abstracting away `IO`) version of:

```scala
new Transformation.AbsorbError[EitherT[IO, *, *], IO] {
      def apply[E, A](fa: EitherT[IO, E, A], injectError: E => Throwable): IO[A] =
        fa.leftMap(injectError).rethrowT
    }
```

and the corresponding `Transformation.SurfaceError` transformation.