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/super/basicmethodSuperTrait.kt

@@ -0,0 +1,14 @@
+
+interface Tr {
+   fun extra() : String = "_"
+}
+
+class N() : Tr {
+   override fun extra() : String = super<Tr>.extra() + super<Tr>.extra()
+}
+
+fun box(): String {
+    val n = N()
+    if (n.extra() == "__") return "OK"
+    return "fail";
+}