runtime: CultureInfo.GetCultures missing in .NET Core

We’re currently building out the support for language resources and i18n/l10n in ASP.NET 5/DNX and we’re wondering why there doesn’t appear to be a way to retrieve a list of all available cultures in .NET Core. Right now it appears our only option for determining if a culture string is valid is to attempt to create a CultureInfo object from it using the CultureInfo(string name) ctor, and catching the resulting CultureNotFoundException if it’s indeed invalid. This feels sub-optimal.