refactor: moving signature logic from ethlambda-types to ethlambda-crypto

[Sahilgill24]

Description / Motivation

porting the lean-sig based signature logic from types crate to crypto crate as mentioned here

It is first of all a cleaner and more idiomatic approach and secondly ethlambda-types crate builds/compiles for the prover crate(zkVM prover), which also leads to dependency conflicts between leansig dependencies and the zkVM sdk dependencies being used. This port removes all leansig dependencies from the ethlambda-types

What Changed

• added a new signature.rs file to the crypto crate along with a extension trait ValidatorPublicKeys with the same methods as before, it helps in avoiding cyclic dependencies and the call sites remain the same.
• removed the older signature.rs from the types crate and moved the SIGNATURE_SIZE directly to the attestation.rs

Verification Checklist

• Ran make fmt
• Ran make lint (clippy with -D warnings)
• Ran cargo test --workspace --release — all passing