intl: increase coverage for NumberFormat constructor

Increase coverage for the Intl.NumberFormat constructor by adding tests
checking if appropriate default values are used.

test/intl402/NumberFormat/constructor-default-value.js

+// Copyright (C) 2018 Ujjwal Sharma. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-initializenumberformat
+description: >
+  Tests that the constructor for Intl.NumberFormat uses appropriate default
+  values for its arguments (locales and options).
+---*/
+
+const actual = new Intl.NumberFormat();
+const expected = new Intl.NumberFormat([], { __proto__: null });
+
+assert.sameValue(actual.resolvedOptions(), expected.resolvedOptions());