Cardano Updates

  The strategy is to map every type from stdlib to its own "general
  fuzzer" taking no argument and yielding a fully arbitrary value; or,
  have `_with` fine-grained fuzzers for each of the type's variants that
  take additional fuzzers as arguments.

  We're also thinking that having those fuzzers check for well-formness
  of data (e.g. policy id is 28 bytes) is a good idea, so that what
  comes out of those is somewhat well-formed data and phase-1
  validations down the line are simplified.