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/arrays/kt945.kt

@@ -0,0 +1,9 @@
+fun box() : String {
+    val data = Array<Array<Boolean>>(3) { Array<Boolean>(4, {false}) }
+    for(d in data) {
+        if(d.size != 4) return "fail"
+        for(b in d) if (b) return "fail"
+    }
+
+    return "OK"
+}