allows for setting randomization with flags, but also modifies the
Options struct to now have two separate values
Overall this relates in a much more understandable UI from a user
perspective, since the normal case for randomization will be a user
just saying “run these out of order please” — and in a rare case they
may wish to additionally supply a seed to try to reproduce an older run
to trigger the same error condition.
This allows for us to propagate the seed value around, and not have to
have two different values in Options when we want to allow
specification of seed. It does introduce some “magic values”, but the
document them in the Options struct docstrings.
