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/ranges/forNullableIntInRangeWithImplicitReceiver.kt

@@ -0,0 +1,20 @@
+// WITH_RUNTIME
+
+import kotlin.test.assertEquals
+
+fun suppressBoxingOptimization(ni: Int?) {}
+
+fun Int.digitsUpto(end: Int): Int {
+    var sum = 0
+    for (i: Int? in rangeTo(end)) {
+        suppressBoxingOptimization(i)
+        sum = sum*10 + i!!
+    }
+    return sum
+}
+
+fun box(): String {
+    assertEquals(1234, 1.digitsUpto(4))
+    return "OK"
+}
+