Rust 1.54.0 lints (#2483)

## Issue Addressed

N/A

## Proposed Changes

- Removing a bunch of unnecessary references
- Updated `Error::VariantError` to `Error::Variant`
- There were additional enum variant lints that I ignored, because I thought our variant names were fine
- removed `MonitoredValidator`'s `pubkey` field, because I couldn't find it used anywhere. It looks like we just use the string version of the pubkey (the `id` field) if there is no index

## Additional Info



Co-authored-by: realbigsean <seananderson33@gmail.com>

testing/ef_tests/src/case_result.rs

@@ -41,7 +41,7 @@ pub fn compare_beacon_state_results_without_caches<T: EthSpec, E: Debug>(
         expected.drop_all_caches().unwrap();
     }
 
-    compare_result_detailed(&result, &expected)
+    compare_result_detailed(result, expected)
 }
 
 /// Same as `compare_result`, however utilizes the `CompareFields` trait to give a list of