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/initializationOrder.kt

@@ -0,0 +1,16 @@
+var result = "OK"
+
+class A {
+    companion object {
+        var z = result
+
+        fun patchResult() {
+            result = "fail"
+        }
+    }
+}
+
+fun box(): String {
+    A.patchResult()
+    return A.z
+}