Use intrinsic info in browse URLs

Currently, the browse web application uses non intrinsic info in URLs to reference origins and their visits. For instance, the root directory as found in the latest visit of the Linux kernel source tree mirror on Github can be browsed through the URL: /browse/origin/2/visit/28/directory/. The problematic parts in this URL are the use of the internal database ids for referencing the origin and its visit.

In order to use intrinsic info, that URL should be replaced by /browse/origin/git/url/https:∕/github.com/torvalds/linux/visit/2017-11-21T19:37:00.000Z/directory

It means that an origin should always be referred by its type and its url while one of its visits by a date (fetching the closest visit when the provided date is not an exact visit one).

That scheme must be used in the whole browse URLs.

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Migrated from T877 (view on Phabricator)