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/defaultArguments/function/extentionFunction.kt

@@ -0,0 +1,9 @@
+fun Int.foo(a: Int = 1): Int {
+    return a
+}
+
+fun box(): String  {
+    if (1.foo() != 1) return "fail"
+    if (1.foo(2) != 2) return "fail"
+    return "OK"
+}