backend/tests: Add blackbox tests from Kotlin JVM

Added tests from testData/codegen/box directory. There are blackbox tests
in other directories and they are to be added.

backend.native/tests/external/codegen/blackbox/objects/objectWithSuperclass.kt

@@ -0,0 +1,16 @@
+open class A {
+    open fun foo(): Int {
+        return 2
+    }
+}
+
+object O: A() {
+    override fun foo(): Int {
+        val s = super<A>.foo()
+        return s + 3
+    }
+}
+
+fun box() : String {
+  return if (O.foo() == 5) "OK" else "fail"
+}