Ref T13546. Show ongoing and failed builds more clearly in "arc land" output.
Also rename "DisplayRef" (which is not a "Ref") to "RefView" with the goal of improving clarity, and let callers "build...()" it so they can add more status, etc., information.
Get rid of "[DisplayRef|RefView]Interface". In theory, future refs (say, in Phabricator) might not do anything here, but every Ref just ends up implementing it. This could perhaps be subclassed more narrowly in the future if necessary.