Add eip_3076 crate (#8206)

#7894


  Moves the `Interchange` format from `slashing_protection` and thus removes the dependency on `slashing_protection` from `eth2` which can now just depend on the slimmer `eip_3076` crate.


Co-Authored-By: Mac L <mjladson@pm.me>

common/eth2/src/lighthouse_vc/std_types.rs

@@ -3,7 +3,7 @@ use serde::{Deserialize, Serialize};
 use types::{Address, Graffiti, PublicKeyBytes};
 use zeroize::Zeroizing;
 
-pub use slashing_protection::interchange::Interchange;
+pub use eip_3076::Interchange;
 
 #[derive(Debug, Deserialize, Serialize, PartialEq)]
 pub struct GetFeeRecipientResponse {