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/basicproperty.kt

@@ -0,0 +1,24 @@
+open class M() {
+    open var b: Int = 0
+}
+
+class N() : M() {
+    val a : Int
+        get() {
+            super.b = super.b + 1
+            return super.b + 1
+        }
+    override var b: Int = a + 1
+
+    val superb : Int
+        get() = super.b
+}
+
+fun box(): String {
+    val n = N()
+    n.a
+    n.b
+    n.superb
+    if (n.b == 3 && n.a == 4 && n.superb == 3) return "OK";
+    return "fail";
+}