Fix Rust beta compiler errors (1.77) (#5180)

* Lint fixes

* More fixes for beta compiler.

* Format fixes

* Move `#[allow(dead_code)]` to field level.

* Remove old comment.

* Update beacon_node/execution_layer/src/test_utils/mod.rs

Co-authored-by: João Oliveira <hello@jxs.pt>

* remove duplicate line

beacon_node/http_api/src/block_packing_efficiency.rs

@@ -19,10 +19,11 @@ use warp_utils::reject::{beacon_chain_error, custom_bad_request, custom_server_e
 const BLOCK_ROOT_CHUNK_SIZE: usize = 100;
 
 #[derive(Debug)]
+// We don't use the inner values directly, but they're used in the Debug impl.
 enum PackingEfficiencyError {
-    BlockReplay(BlockReplayError),
-    BeaconState(BeaconStateError),
-    CommitteeStoreError(Slot),
+    BlockReplay(#[allow(dead_code)] BlockReplayError),
+    BeaconState(#[allow(dead_code)] BeaconStateError),
+    CommitteeStoreError(#[allow(dead_code)] Slot),
     InvalidAttestationError,
 }