Qt NSPhotoLibrarySupport should use Photos Framework replacing deprecated AssetsLibrary Framework

NSPhotoLibrarySupport should use the Photos Framework as the AssetsLibrary Framework has been deprecated since iOS 9 and tvOS 9.

https://developer.apple.com/documentation/assetslibrary/alassetslibrary

This affects how URLs to assets in the Photos library are created.

The problem associated with creating URLs to assets was originally reported by ekke on the interest@qt-project.org mailing list:

http://lists.qt-project.org/pipermail/interest/2017-October/028443.html

The relevant code is under:

qtbase/src/plugins/platforms/ios/optional/nsphotolibrarysupport