Use E for EthSpec globally (#5264)

* Use `E` for `EthSpec` globally

* Fix tests

* Merge branch 'unstable' into e-ethspec

* Merge branch 'unstable' into e-ethspec

# Conflicts:
#	beacon_node/execution_layer/src/engine_api.rs
#	beacon_node/execution_layer/src/engine_api/http.rs
#	beacon_node/execution_layer/src/engine_api/json_structures.rs
#	beacon_node/execution_layer/src/test_utils/handle_rpc.rs
#	beacon_node/store/src/partial_beacon_state.rs
#	consensus/types/src/beacon_block.rs
#	consensus/types/src/beacon_block_body.rs
#	consensus/types/src/beacon_state.rs
#	consensus/types/src/config_and_preset.rs
#	consensus/types/src/execution_payload.rs
#	consensus/types/src/execution_payload_header.rs
#	consensus/types/src/light_client_optimistic_update.rs
#	consensus/types/src/payload.rs
#	lcli/src/parse_ssz.rs

consensus/state_processing/src/per_epoch_processing/slashings.rs

@@ -3,8 +3,8 @@ use safe_arith::{SafeArith, SafeArithIter};
 use types::{BeaconState, BeaconStateError, ChainSpec, EthSpec, Unsigned};
 
 /// Process slashings.
-pub fn process_slashings<T: EthSpec>(
-    state: &mut BeaconState<T>,
+pub fn process_slashings<E: EthSpec>(
+    state: &mut BeaconState<E>,
     total_balance: u64,
     spec: &ChainSpec,
 ) -> Result<(), Error> {
@@ -19,7 +19,7 @@ pub fn process_slashings<T: EthSpec>(
     let (validators, balances, _) = state.validators_and_balances_and_progressive_balances_mut();
     for (index, validator) in validators.iter().enumerate() {
         if validator.slashed
-            && epoch.safe_add(T::EpochsPerSlashingsVector::to_u64().safe_div(2)?)?
+            && epoch.safe_add(E::EpochsPerSlashingsVector::to_u64().safe_div(2)?)?
                 == validator.withdrawable_epoch
         {
             let increment = spec.effective_balance_increment;