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_block_processing/verify_deposit.rs

@@ -30,8 +30,8 @@ pub fn verify_deposit_signature(deposit_data: &DepositData, spec: &ChainSpec) ->
 /// otherwise returns `None`.
 ///
 /// Builds the pubkey cache if it is not already built.
-pub fn get_existing_validator_index<T: EthSpec>(
-    state: &mut BeaconState<T>,
+pub fn get_existing_validator_index<E: EthSpec>(
+    state: &mut BeaconState<E>,
     pub_key: &PublicKeyBytes,
 ) -> Result<Option<u64>> {
     let validator_index = state.get_validator_index(pub_key)?;
@@ -44,8 +44,8 @@ pub fn get_existing_validator_index<T: EthSpec>(
 /// before they're due to be processed, and in parallel.
 ///
 /// Spec v0.12.1
-pub fn verify_deposit_merkle_proof<T: EthSpec>(
-    state: &BeaconState<T>,
+pub fn verify_deposit_merkle_proof<E: EthSpec>(
+    state: &BeaconState<E>,
     deposit: &Deposit,
     deposit_index: u64,
     spec: &ChainSpec,