The original, now obsoleted, `LocalizedString` API returned a .net
`string` which does not work in most cases.
Different versions of iOS seems to return different (public or internal)
subclasses of `NSString` that are understood by other API (like NSString
`localizedStringWithFormat:`) for further customization.
Our logic to convert NSString to string is correct but it cannot
recreate the custom, required subclass to continue the localization.
So the new API return an `NSString` publicly (which is actually a
subclass) that can do the required job.
Adding a test in monotouch-test is presently blocked by #3265 [2]
[1] https://bugzilla.xamarin.com/show_bug.cgi?id=41292
[2] https://github.com/xamarin/xamarin-macios/issues/3265
* Add tests for new (and old) NSBundle API and adjust old ones since adding a Base.lproj directories changes things
* Add localization to xammac_tests since it shares the same, updated tests