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/inRangeConditionsInWhen.kt

@@ -0,0 +1,8 @@
+fun Int.contains(i : Int) = true
+
+fun box(): String {
+    when (1) {
+        in 2 -> return "OK"
+        else -> return "fail"
+    }
+}