Refactor consensus/types (#7827)

Organize and categorize `consensus/types` into modules based on their relation to key consensus structures/concepts.
This is a precursor to a sensible public interface.

While this refactor is very opinionated, I am open to suggestions on module names, or type groupings if my current ones are inappropriate.


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

common/eth2/src/lighthouse_vc/types.rs

@@ -2,7 +2,6 @@ pub use crate::lighthouse::Health;
 pub use crate::lighthouse_vc::std_types::*;
 pub use crate::types::{GenericResponse, VersionData};
 use eth2_keystore::Keystore;
-use graffiti::GraffitiString;
 use serde::{Deserialize, Serialize};
 use std::path::PathBuf;
 pub use types::*;