Support error type elimination within try-catch clauses

[rfmejia]

To improve the ergonomics of error handling, it would be nice if we could eliminate some union types from the error channel when explicitly handled in a catch block. Maybe we can simulate the symantics of ZIO.catchSome and ZIO.die:

import zio.*
import zio.direct.*

case class ID()
case class Person()
case class ParseError()
case class DBError()

def parseId(s: String): IO[ParseError, ID] = ???
def getPerson(id: ID): IO[DBError, Person] = ???

val t: IO[DBError, Person] = defer {
  try {
    val id = parseId("1").run
    getPerson(id).run
  } // ZIO[Any, DBError | ParseError, Person]
  catch { 
    case v: ParseError => Person()  // eliminate ParseError we return a subtype of Person (simulates ZIO.catchSome)
    case v: ParseError => ZIO.die(???)  // alternatively, terminate the fiber with a defect
  }
}