intl: increase coverage for the NumberFormat constructor

Increase coverage for the Intl.NumberFormat constructor by testing that
passing a string value to the Intl.NumberFormat constructor is
equivalent to passing an Array containing the same string value.

test/intl402/NumberFormat/constructor-locales-string.js

@@ -0,0 +1,19 @@
+// 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 passing a string value to the Intl.NumberFormat constructor is
+  equivalent to passing an Array containing the same string value.
+info: |
+  9.2.1 CanonicalizeLocaleList ( locales )
+
+  3 .If Type(locales) is String, then
+    a. Let O be CreateArrayFromList(« locales »).
+---*/
+
+const actual = Intl.NumberFormat('en-US');
+const expected = Intl.NumberFormat(['en-US']);
+
+assert.sameValue(actual.resolvedOptions(), expected.resolvedOptions());