[K/N][Tests] Adjust moved codegen tests to new infra

^KT-61259

native/native.tests/testData/codegen/basics/unchecked_cast2.kt

@@ -2,18 +2,16 @@
  * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
  * that can be found in the LICENSE file.
  */
-
-package codegen.basics.unchecked_cast2
+// IGNORE_BACKEND: NATIVE
 
 import kotlin.test.*
 
-@Test
-fun runTest() {
+fun box(): String {
     try {
         val x = cast<String>(Any())
-        println(x.length)
+        return "FAIL: ${x.length}"
     } catch (e: Throwable) {
-        println("Ok")
+        return "OK"
     }
 }