Test vectors for blake2b with various digest sizes. As the algorithm is
the same up to the digest calculation, the key and input data length is
distributed in a way that tests all combinanions of the two over the
digest sizes.
Based on the suggestion from Eric, the following input sizes are tested
[0, 1, 7, 15, 64, 247, 256], where blake2b blocksize is 128, so the
padded and the non-padded input buffers are tested.