Address clippy lints in tree-states (#4414)

* Address some clippy lints

* Box errors to fix error size lint

* Add Default impl for Validator

* Address more clippy lints

* Re-implement `check_state_diff`

* Fix misc test compile errors

testing/ef_tests/src/cases/epoch_processing.rs

@@ -328,7 +328,7 @@ impl<E: EthSpec, T: EpochTransition<E>> Case for EpochProcessing<E, T> {
 
         let mut result = T::run(&mut state, spec).map(|_| state);
 
-        check_state_diff(&pre_state, &expected)?;
+        check_state_diff(&pre_state, &expected, spec)?;
         compare_beacon_state_results_without_caches(&mut result, &mut expected)
     }
 }

testing/ef_tests/src/cases/operations.rs

@@ -458,7 +458,7 @@ impl<E: EthSpec, O: Operation<E>> Case for Operations<E, O> {
         // NOTE: some of the withdrawals tests have 0 active validators, do not try
         // to build the commitee cache in this case.
         if O::handler_name() != "withdrawals" {
-            state.build_all_committee_caches(spec).unwrap();
+            pre_state.build_all_committee_caches(spec).unwrap();
         }
 
         let mut state = pre_state.clone();
@@ -475,7 +475,7 @@ impl<E: EthSpec, O: Operation<E>> Case for Operations<E, O> {
             .apply_to(&mut state, spec, self)
             .map(|()| state);
 
-        check_state_diff(&pre_state, &expected)?;
+        check_state_diff(&pre_state, &expected, spec)?;
         compare_beacon_state_results_without_caches(&mut result, &mut expected)
     }
 }

testing/ef_tests/src/cases/sanity_blocks.rs

@@ -137,7 +137,7 @@ impl<E: EthSpec> Case for SanityBlocks<E> {
             post.build_all_committee_caches(spec).unwrap();
             post
         });
-        check_state_diff(&pre, &post)?;
+        check_state_diff(&pre, &post, spec)?;
         Ok(())
     }
 }

testing/ef_tests/src/cases/sanity_slots.rs

@@ -76,6 +76,6 @@ impl<E: EthSpec> Case for SanitySlots<E> {
             post.build_all_committee_caches(spec).unwrap();
             post
         });
-        check_state_diff(&pre, &post)
+        check_state_diff(&pre, &post, spec)
     }
 }