Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/super/enclosedVar.kt

@@ -0,0 +1,22 @@
+open class M() {
+    open var y = 500
+}
+
+open class N() : M() {
+
+    override var y = 200
+
+    open inner class C() {
+        fun test5() = y
+        fun test6() : Int {
+            super<M>@N.y += 200
+            return super<M>@N.y
+        }
+    }
+}
+
+fun box(): String {
+    if (N().C().test5() != 200) return "test5 fail";
+    if (N().C().test6() != 700) return "test6 fail";
+    return "OK";
+}