Fix tree-states tests after latest update (#5528)

* Fix clippy

* Fix beacon chain tests

* Comment out dodgy iterator test

* Fix imports for beta compiler

consensus/state_processing/src/per_block_processing/errors.rs

@@ -1,5 +1,5 @@
 use super::signature_sets::Error as SignatureSetError;
-use crate::{ContextError, EpochCacheError};
+use crate::ContextError;
 use merkle_proof::MerkleTreeError;
 use safe_arith::ArithError;
 use ssz::DecodeError;

consensus/state_processing/src/per_block_processing/process_operations.rs

@@ -5,7 +5,6 @@ use crate::common::{
 };
 use crate::per_block_processing::errors::{BlockProcessingError, IntoWithIndex};
 use crate::VerifySignatures;
-use safe_arith::SafeArith;
 use std::sync::Arc;
 use types::consts::altair::{PARTICIPATION_FLAG_WEIGHTS, PROPOSER_WEIGHT, WEIGHT_DENOMINATOR};