dmrun: move from x/devtools to x/ref
dmrun: move from x/devtools to x/ref

dmrun is not really a development tool. Besides, keeping in devtools breaks the
devtools depcop rule.  x/ref is not a great place either, but seems the most
suitable among the options.

MultiPart: 1/2
Change-Id: I9bd170181b323700cd1c37753cc066b864353e0a

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools