Remove the std::mem::transmute when getting NsTable in Rust espresso crypto

[ImJeremyHe]

nitro-espresso-integration/espressocrypto/lib/espresso-crypto-helper/src/lib.rs

Line 101 in 9f75472

let ns_table: NsTable = unsafe { std::mem::transmute(ns_table_bytes.to_vec()) };

I think we can marshal the NsTable to JSON first and deserialize it again in Rust. This will lead to a worse performance though, getting rid of unsafe should worth it as we can get more debug information.
Or adding a method NsTable::from_bytes in sequencer repo is even a better alternative, if there is no side effect in sequencer