Impl 16-bytes output hash/aes functions

The LABLE SIZE is 16, and we just truncate the 32-byte output to 16 by getting the higher half. It's not safe. 

Code: https://github.com/GOATNetwork/bitvm2-gc/blob/main/garbled-snark-verifier/src/core/utils.rs#L53.

One option:  AES NI. It's efficient, but there is no precompile yet.
 