Rust 1.71 lints (#4503)

## Issue Addressed

N/A

## Proposed Changes

Add lints for rust 1.71

[3789134](3789134ae2) is probably the one that needs most attention as it changes beacon state code. I changed the `is_in_inactivity_leak ` function to return a `ArithError` as not all consumers of that function work well with a `BeaconState::Error`.

beacon_node/http_api/src/block_packing_efficiency.rs

@@ -75,7 +75,7 @@ impl<T: EthSpec> PackingEfficiencyHandler<T> {
             available_attestations: HashSet::new(),
             included_attestations: HashMap::new(),
             committee_store: CommitteeStore::new(),
-            _phantom: PhantomData::default(),
+            _phantom: PhantomData,
         };
 
         handler.compute_epoch(start_epoch, &starting_state, spec)?;