Rust clippy 1.87 lint fixes (#7471)

Fix clippy lints for `rustc` 1.87


  clippy complains about `BeaconChainError` being too large. I went on a bit of a boxing spree because of this. We may instead want to `Box` some of the `BeaconChainError` variants?

beacon_node/beacon_chain/src/eth1_finalization_cache.rs

@@ -100,22 +100,13 @@ impl CheckpointMap {
 
 /// This cache stores `Eth1CacheData` that could potentially be finalized within 4
 /// future epochs.
+#[derive(Default)]
 pub struct Eth1FinalizationCache {
     by_checkpoint: CheckpointMap,
     pending_eth1: BTreeMap<u64, Eth1Data>,
     last_finalized: Option<Eth1Data>,
 }
 
-impl Default for Eth1FinalizationCache {
-    fn default() -> Self {
-        Self {
-            by_checkpoint: CheckpointMap::new(),
-            pending_eth1: BTreeMap::new(),
-            last_finalized: None,
-        }
-    }
-}
-
 /// Provides a cache of `Eth1CacheData` at epoch boundaries. This is used to
 /// finalize deposits when a new epoch is finalized.
 ///