[SPARK-3944][Core] Using Option[String] where value of String can be null

Sorry for being late on this, but I'd really rather not see things like `case Some("http") | Some("https") | Some("ftp") =>`.  Instead, I'd do this as:
```scala
Option(uri.getScheme).getOrElse("file") match {
  case "http" | "https" | "ftp" => ...
  case "file" => ...
  case _ =>
}
```