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/store/src/hot_cold_store.rs

@@ -1344,7 +1344,7 @@ impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold>
         high_restore_point
             .get_block_root(slot)
             .or_else(|_| high_restore_point.get_oldest_block_root())
-            .map(|x| *x)
+            .copied()
             .map_err(HotColdDBError::RestorePointBlockHashError)
     }