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/dataClasses/copy/copyInObjectNestedDataClass.kt

@@ -0,0 +1,17 @@
+class Bar(val name: String)
+
+abstract class Foo {
+  public abstract fun foo(): String
+}
+
+fun box(): String {
+    return object: Foo() {
+      inner class NestedFoo(val bar: Bar) {
+          fun copy(bar: Bar) = NestedFoo(bar)
+      }
+
+      override fun foo(): String {
+        return NestedFoo(Bar("Fail")).copy(bar = Bar("OK")).bar.name
+      }
+    }.foo()
+}