mass: return memory report to arvo

[tinnus-napbus]

Dill can give Vere a [%quac ~] gift and vere returns a memory report in a [%quac p=(list quac)] where a quac is a [name=@t size=@ud quacs=(list quac)] nested memory report structure. Vere itself does not print the memory report in this case, but it still does when requested with the old |mass/%heft and grab from the command-line. Arvo will implement its own memory report printer for quacs.

Unlike the previous version that used a fake driver to inject the report, this does it properly through Dill's driver, using a %quiz plea/writ to query the serf for this info.