swh-web/browse: Add shorter url scheme for origin-context views

Currently, when browsing archive objects in a context of an origin, the used urls are prefixed by /browse/origin/(origin_type)/url/(origin_url)/...

While maintanining the current scheme, shorter url prefix /browse/origin/(origin_url)/... could also be used. Under the hood, a simple routine checking which type of origin is related to the url will be implemented and used.