Backport: Support for getting all possible links for a document within a channel

Currently, you can get for a document the canonical link for all channels that have a sitemap item with a relative content path that can match that document. However, it is not possible to get all available sitemap items (all links) that can be created for that document within a single channel.

Note that only links with a sitemap item that can resolve to the document are returned. If the document for example is also used in some list (say latest three news articles on the homepage), the URL that happens to show that list is not returned