This is not intended to be a completed transition since it leaves the
libraries unusable to external client code, but rather as a step towards
use of math/rand/v2. This initial step allows repair of sequence change
failures without having to worry about API difference.
Tests run repeatedly do not reinitialise state, meaning that a second run
of the tests will have leftover state from the previous run. This ensures
that repeated runs are identical with the exception of map iteration order.
