Best of both worlds, this allows for a single int64 value in the
Options struct, but at the same time we can do `—random` from command
line with no args and have a default value Chosen.
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.
