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/functions/recursiveCompareTo.kt

@@ -0,0 +1,11 @@
+class C
+
+operator fun C.compareTo(o: C) : Int {
+    if (this == o) return 0
+    if (o >= o) {
+        return 1
+    }
+    return -1
+}
+
+fun box() : String = if (C() > C()) "OK" else "FAIL"