Add support for checked casts in debug mode

[Duhemm]

The following code compiles fine, but its behavior is different on the JVM and on Native:

object Main {
  def main(args: Array[String]): Unit = {
    println(0.asInstanceOf[String]) // Prints `0`, should throw `ClassCastException`
    println("" + 0.asInstanceOf[String]) // Prints ``, should throw `ClassCastException`
  }
}

On Native, the first println will print 0, but it should throw an exception.
The second println will print an empty line, but it should throw an exception too.

[densh]

Casts are unchecked on purpose in release mode. We wanted to make them checked in debug for a while now, but there was no issue for it.

[densh]

Superseded by #1140