Fix ecrecover method in signature.rs

[flodesi]

Task summary
Currently, the ecrecover method in signature.rs is panicking due to incorrect code whenever this function is called. This issue will fix this problem as well as update the logic to correctly get an Address given a message hash and Signature.

Specification reference
Refer to go-secp256k1: https://github.com/ipsn/go-secp256k1/blob/9d62b9f0bc52d16160f79bfb84b2bbf0f6276b03/secp256.go#L93
as well as Zondax: https://github.com/Zondax/filecoin-rs/blob/842f61de3c6c3d5d90c5b2ada9d1e342331fe23f/signer/src/lib.rs#L315