RPC: Run each benchmarked RPC in its own vtrace trace.
RPC: Run each benchmarked RPC in its own vtrace trace.

This makes analyzing rpc timing with vtrace much more effective and
performant.

Change-Id: I7b96b312a75c594879d3c1897b6b4b34c28f10e9

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref