Clippy clean (#536)

* Change into_iter to iter

* Fix clippy 'easy' warnings

* Clippy eth2/utils

* Add struct NetworkInfo

* Clippy for types, utils, and beacon_node/store/src/iters.rs

* Cargo fmt

* Change foo to my_foo

* Remove complex signature

* suppress clippy warning for unit_value in benches

* Use enumerate instead of iterating over range

* Allow trivially_copy_pass_by_ref in serde_utils

eth2/state_processing/src/per_block_processing/verify_attestation.rs

@@ -130,6 +130,6 @@ fn verify_casper_ffg_vote<'a, T: EthSpec>(
         );
         Ok(state.get_previous_crosslink(data.crosslink.shard)?)
     } else {
-        return Err(error(Invalid::BadTargetEpoch));
+        Err(error(Invalid::BadTargetEpoch))
     }
 }