feat: nonzero `DataHasher`

[Autoparallel]

• [x] Creates a DataHasher that does not hash a chunk of 16 bytes if they are ALL zero.

Reasoning

We want to be able to just AES encrypt 200 bytes and use the ciphertext from the server if we are going to use the 512b circuits. Without this, we need to AES encrypt 512b so that the use of DataHasher in HttpNIVC would match. Now HttpNIVC ignores 0 padding at the end of bytes and will only hash the relevant plaintext bytes (e.g., in our example: 200b).

[lonerapier]

rebased it from main, merging it after CI runs green