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/forLoopMemberExtensionHasNext.kt

@@ -0,0 +1,26 @@
+class It {
+    fun next() = 5
+}
+
+class C {
+    fun iterator(): It = It()
+}
+
+class X {
+    var hasNext = true
+    fun It.hasNext() = if (hasNext) {hasNext = false; true} else false
+
+    fun test() {
+        for (i in C()) {
+            foo(i)
+        }
+    }
+
+}
+
+fun foo(x: Int) {}
+
+fun box(): String {
+    X().test()
+    return "OK"
+}