Move blackBoxFile() testData to box/ directory

Delete all test methods (and empty test classes), since they'll be
auto-generated

compiler/testData/codegen/box/controlStructures/longRange.kt

@@ -0,0 +1,8 @@
+fun box(): String {
+  val r = 1.toLong()..2
+  var s = ""
+  for (l in r) {
+    s += l
+  }
+  return if (s == "12") "OK" else "fail: $s"
+}