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/registry_updates.rs

@@ -6,8 +6,8 @@ use types::{BeaconState, ChainSpec, EthSpec, Validator};
 /// Performs a validator registry update, if required.
 ///
 /// NOTE: unchanged in Altair
-pub fn process_registry_updates<T: EthSpec>(
-    state: &mut BeaconState<T>,
+pub fn process_registry_updates<E: EthSpec>(
+    state: &mut BeaconState<E>,
     spec: &ChainSpec,
 ) -> Result<(), Error> {
     // Process activation eligibility and ejections.