1.57.0 lints (#2850)

## Issue Addressed

New rust lints

## Proposed Changes

- Boxing some enum variants
- removing some unused fields (is the validator lockfile unused? seemed so to me)

## Additional Info

- some error fields were marked as dead code but are logged out in areas
- left some dead fields in our ef test code because I assume they are useful for debugging?

Co-authored-by: realbigsean <seananderson33@gmail.com>

common/eth2/src/types.rs

@@ -777,7 +777,7 @@ pub struct SseLateHead {
 #[derive(PartialEq, Debug, Serialize, Clone)]
 #[serde(bound = "T: EthSpec", untagged)]
 pub enum EventKind<T: EthSpec> {
-    Attestation(Attestation<T>),
+    Attestation(Box<Attestation<T>>),
     Block(SseBlock),
     FinalizedCheckpoint(SseFinalizedCheckpoint),
     Head(SseHead),