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/when/switchOptimizationUnordered.kt

@@ -0,0 +1,17 @@
+// WITH_RUNTIME
+
+fun foo(x: Int): Int {
+    return when (x) {
+        2 -> 6
+        1 -> 5
+        3 -> 7
+        else -> 8
+    }
+}
+
+fun box(): String {
+    var result = (0..3).map(::foo).joinToString()
+
+    if (result != "8, 5, 6, 7") return "unordered:" + result
+    return "OK"
+}