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

beacon_node/lighthouse_network/src/peer_manager/peerdb/score.rs

@@ -186,14 +186,7 @@ impl RealScore {
 
     /// Add an f64 to the score abiding by the limits.
     fn add(&mut self, score: f64) {
-        let mut new_score = self.lighthouse_score + score;
-        if new_score > MAX_SCORE {
-            new_score = MAX_SCORE;
-        }
-        if new_score < MIN_SCORE {
-            new_score = MIN_SCORE;
-        }
-
+        let new_score = (self.lighthouse_score + score).clamp(MIN_SCORE, MAX_SCORE);
         self.set_lighthouse_score(new_score);
     }
 

beacon_node/lighthouse_network/src/rpc/codec/ssz_snappy.rs

@@ -443,7 +443,7 @@ fn handle_length(
         // Note: length-prefix of > 10 bytes(uint64) would be a decoding error
         match uvi_codec.decode(bytes).map_err(RPCError::from)? {
             Some(length) => {
-                *len = Some(length as usize);
+                *len = Some(length);
                 Ok(Some(length))
             }
             None => Ok(None), // need more bytes to decode length

beacon_node/lighthouse_network/src/service/gossipsub_scoring_parameters.rs

@@ -270,11 +270,11 @@ impl<TSpec: EthSpec> PeerScoreSettings<TSpec> {
 
         let modulo_smaller = max(
             1,
-            smaller_committee_size / self.target_aggregators_per_committee as usize,
+            smaller_committee_size / self.target_aggregators_per_committee,
         );
         let modulo_larger = max(
             1,
-            (smaller_committee_size + 1) / self.target_aggregators_per_committee as usize,
+            (smaller_committee_size + 1) / self.target_aggregators_per_committee,
         );
 
         Ok((

beacon_node/lighthouse_network/src/service/utils.rs

@@ -88,7 +88,7 @@ fn keypair_from_hex(hex_bytes: &str) -> error::Result<Keypair> {
         hex_bytes.to_string()
     };
 
-    hex::decode(&hex_bytes)
+    hex::decode(hex_bytes)
         .map_err(|e| format!("Failed to parse p2p secret key bytes: {:?}", e).into())
         .and_then(keypair_from_bytes)
 }