Function sig_decode 

pub fn sig_decode<P: Params>(
    sig: &[u8],
) -> Option<(Vec<u8>, [[i32; 256]; 7], [[i32; 256]; 8])>

Decode a signature from bytes.

Implements Algorithm 27 of FIPS 204 (sigDecode). Inverse of sig_encode.

Returns Some((c_tilde, z, h)) on success, or None if the hint encoding is malformed. Uses fixed arrays instead of Vec.