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/kt3114.kt

@@ -0,0 +1,13 @@
+class KeySpan(val left: String) {
+
+    public fun matches(value : String) : Boolean {
+
+        return left > value && left > value
+    }
+
+}
+
+fun box() : String {
+  KeySpan("1").matches("3")
+  return "OK"
+}