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/builtinStubMethods/extendJavaCollections/hashSet.kt

@@ -0,0 +1,18 @@
+class A : HashSet<Long>()
+
+fun box(): String {
+    val a = A()
+    val b = A()
+
+    a.iterator()
+
+    a.add(0L)
+    a.remove(0L)
+
+    a.addAll(b)
+    a.removeAll(b)
+    a.retainAll(b)
+    a.clear()
+
+    return "OK"
+}