Clippy lints for rust 1.66 (#3810)

## Issue Addressed
Fixes the new clippy lints for rust 1.66

## Proposed Changes

Most of the changes come from:
- [unnecessary_cast](https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast)
- [iter_kv_map](https://rust-lang.github.io/rust-clippy/master/index.html#iter_kv_map)
- [needless_borrow](https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow)

## Additional Info

na

consensus/types/src/beacon_state.rs

@@ -482,7 +482,7 @@ impl<T: EthSpec> BeaconState<T> {
     /// Spec v0.12.1
     pub fn get_committee_count_at_slot(&self, slot: Slot) -> Result<u64, Error> {
         let cache = self.committee_cache_at_slot(slot)?;
-        Ok(cache.committees_per_slot() as u64)
+        Ok(cache.committees_per_slot())
     }
 
     /// Compute the number of committees in an entire epoch.

consensus/types/src/beacon_state/committee_cache.rs

@@ -144,7 +144,7 @@ impl CommitteeCache {
             self.committees_per_slot as usize,
             index as usize,
         );
-        let committee = self.compute_committee(committee_index as usize)?;
+        let committee = self.compute_committee(committee_index)?;
 
         Some(BeaconCommittee {
             slot,

consensus/types/src/beacon_state/tests.rs

@@ -344,12 +344,7 @@ mod committees {
 
         let cache_epoch = cache_epoch.into_epoch(state_epoch);
 
-        execute_committee_consistency_test(
-            new_head_state,
-            cache_epoch,
-            validator_count as usize,
-            spec,
-        );
+        execute_committee_consistency_test(new_head_state, cache_epoch, validator_count, spec);
     }
 
     async fn committee_consistency_test_suite<T: EthSpec>(cached_epoch: RelativeEpoch) {
@@ -361,18 +356,13 @@ mod committees {
             .mul(spec.target_committee_size)
             .add(1);
 
-        committee_consistency_test::<T>(validator_count as usize, Epoch::new(0), cached_epoch)
+        committee_consistency_test::<T>(validator_count, Epoch::new(0), cached_epoch).await;
+
+        committee_consistency_test::<T>(validator_count, T::genesis_epoch() + 4, cached_epoch)
             .await;
 
         committee_consistency_test::<T>(
-            validator_count as usize,
-            T::genesis_epoch() + 4,
-            cached_epoch,
-        )
-        .await;
-
-        committee_consistency_test::<T>(
-            validator_count as usize,
+            validator_count,
             T::genesis_epoch()
                 + (T::slots_per_historical_root() as u64)
                     .mul(T::slots_per_epoch())

consensus/types/src/preset.rs

@@ -202,7 +202,7 @@ mod test {
     }
 
     fn preset_from_file<T: DeserializeOwned>(preset_name: &str, filename: &str) -> T {
-        let f = File::open(&presets_base_path().join(preset_name).join(filename))
+        let f = File::open(presets_base_path().join(preset_name).join(filename))
             .expect("preset file exists");
         serde_yaml::from_reader(f).unwrap()
     }