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/traitproperty.kt

@@ -0,0 +1,31 @@
+trait M {
+    var backingB : Int
+    var b : Int
+        get() = backingB
+        set(value: Int) {
+            backingB = value
+        }
+}
+
+class N() : M {
+    public override var backingB : Int = 0
+
+    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";
+}