nara: swedish for near, provides a trace from the start of the nearest virtualization
to the statement wrapped by the nara hint.
hela: swedish for whole, provides a trace from the start of the event
to the statement wrapped by the hela hint.
The eventual goal is to present these traces in a way that is most salient & useful to developers
and in a way that is aesthetically pleasing as the bout hint is useful and nice looking.
For this pull request the goal is to provide the actual functionality in code that we can feel
safe and comfortable adding to the master branch. To this end, I've added a trivial set of tests for
nara and hela in pkg/arvo/tests/run/hints.hoon - they only prove that invoking these hints will not
crash the runtime, but I'm open to ideas for how I can test these hints further.
