Add 1536 and 4096-byte Adiantum test vectors so that the case where
there are multiple NH hashes is tested.  This is already tested by the
nhpoly1305 test vectors, but it should be tested at the Adiantum level
too.  Moreover the 4096-byte case is especially important.

As with the other Adiantum test vectors, these were generated by the
reference Python implementation at https://github.com/google/adiantum
and then automatically formatted for testmgr by a script.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>