Currently, running individual cram tests requires remembering that every test has an alias. Moreover, one also has to qualify the alias with a directory if there's more than one test with the same name. It would be much simpler if we could just pass the test's path to dune runtest and get it to run.

I think this is also useful for justifying the existence of dune runtest itself. Currently, it's just clone of dune build @runtest