🛠️ [TASK] : ElGamal encryption

[Mr-Leshiy]

Summary

Add a lifted ElGamal encryption algorithm into the catalyst-voting crate

Description

Move the necessary code from this file https://github.com/input-output-hk/catalyst-core/blob/f17b5103f8529b5efe05ecb1564d182bbae136ed/src/chain-libs/chain-vote/src/cryptography/elgamal.rs#L3,
needed functionality is encrypted and decrypted functions