Add attemptT variant accepting a partial function

I sometimes find myself trying to recover some Throwables as Left in EitherT. It gets noisy:

val doSomething: IO[Foo] = ???
val doSomething0: EitherT[IO, MyError, Foo] =
  EitherT(
    doSomething.map(_.asRight).recover {
      case e: IOException => MyError(e).asLeft
      case e: SQLException => MyError(e).asLeft
    }
  )

It would be nice to have a combinator that would encapsulate this pattern:

doSomething.attemptPartialT {
  case e: IOException => MyError(e)
  case e: SQLException => MyError(e)
}

We can also have an Either version of it, as a more general version of attemptNarrow.

Start by locating the existing attemptNarrow implementation and the EitherT APIs involved in the example. Compare how the proposed partial-function forms should relate to those entry points, then add coverage for the IOException and SQLException cases and verify that unmatched Throwables retain the expected behavior.