Ref T11137. This class is removed in D16099. Depends on D16099.
PhutilURI now attempts to "just work" with Git-style URIs, so at least in theory we can just delete all of this code and pretend it does not exist.
(I've left "Display URI" and "Effective URI" as distinct, at least for now, because I think the distinction may be relevant in the future even though it isn't right now, and to keep this diff small, although I may go remove one after I think about this for a bit.)