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/classes/initializerBlockDImpl.kt

@@ -0,0 +1,18 @@
+// WITH_RUNTIME
+class World() {
+  public val items: ArrayList<Item> = ArrayList<Item>()
+
+  inner class Item() {
+    init {
+      items.add(this)
+    }
+  }
+
+  val foo = Item()
+}
+
+fun box() : String {
+  val w = World()
+  if (w.items.size != 1) return "fail"
+  return "OK"
+}