Use ASTARTE_UTIL_DEFINE_ARRAY to also generate astarte_binary_arrays_t

[lucaato]

Low-priority issue. To keep consistency in our astarte value APIs, we should refactor the way we serialize binary blob arrays to allow the user to pass in an array struct (generated using ASTARTE_UTIL_DEFINE_ARRAY(astarte_binaryblob_array_t, astarte_binaryblob_t)).
Currently, we are taking as argument an array of pointers, an array of lengths, and the length of the two arrays. It would be more consistent to use our array type again.
This issue references an inline comment.