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/controlStructures/forIntArray.kt

@@ -0,0 +1,14 @@
+fun box() : String {
+    val a = arrayOfNulls<Int>(5)
+    var i = 0
+    var sum = 0
+    for(el in 0..4) {
+       a[i] = i++
+    }
+    for (el in (a as Array<Int>)) {
+        sum = sum + el
+    }
+    if(sum != 10) return "a failed"
+
+    return "OK"
+}