As of this commit, this only affects the Sapling test vectors (we still sample the same
randomness to avoid disturbing the others).
A "diversifier_index" field is added to the Unified Address test vectors. (This is not needed
for UIVKs/UFVKs since they do not depend on the diversifier index for any protocol.)
We also add an "account" field to make the account number explicit, even though it could be
inferred from the test vector index.
Signed-off-by: Daira Hopwood <daira@jacaranda.org>