Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/classes/funDelegation.kt

@@ -0,0 +1,17 @@
+open class Base() {
+    fun n(n : Int) : Int = n + 1
+}
+
+trait Abstract {}
+
+class Derived1() : Base(), Abstract {}
+class Derived2() : Abstract, Base() {}
+
+fun test(s : Base) : Boolean = s.n(238) == 239
+
+fun box() : String {
+    if (!test(Base())) return "Fail #1"
+    if (!test(Derived1())) return "Fail #2"
+    if (!test(Derived2())) return "Fail #3"
+    return "OK"
+}