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/objects/kt3238.kt

@@ -0,0 +1,15 @@
+// TODO: muted automatically, investigate should it be ran for JS or not
+// IGNORE_BACKEND: JS
+
+object Obj {
+    class Inner() {
+        fun ok() = "OK"
+    }
+}
+
+fun box() : String {
+    val klass = Class.forName("Obj\$Inner")!!
+    val cons = klass.getConstructors()!![0]
+    val inner = cons.newInstance(*(arrayOfNulls<String>(0) as Array<String>))
+    return "OK"
+}