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/lazyCodegen/when.kt

@@ -0,0 +1,15 @@
+class A (val p: String) {
+
+    val _kind: String = when {
+        p == "test" -> "OK"
+        else -> "fail"
+    }
+
+}
+
+fun box(): String {
+
+    if (A("test")._kind != "OK") return "fail"
+
+    return "OK"
+}