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/state_advance.rs

@@ -25,8 +25,8 @@ pub enum Error {
 ///
 /// This state advance method is "complete"; it outputs a perfectly valid `BeaconState` and doesn't
 /// do anything hacky like the "partial" method (see `partial_state_advance`).
-pub fn complete_state_advance<T: EthSpec>(
-    state: &mut BeaconState<T>,
+pub fn complete_state_advance<E: EthSpec>(
+    state: &mut BeaconState<E>,
     mut state_root_opt: Option<Hash256>,
     target_slot: Slot,
     spec: &ChainSpec,
@@ -58,8 +58,8 @@ pub fn complete_state_advance<T: EthSpec>(
 ///
 /// - If `state.slot > target_slot`, an error will be returned.
 /// - If `state_root_opt.is_none()` but the latest block header requires a state root.
-pub fn partial_state_advance<T: EthSpec>(
-    state: &mut BeaconState<T>,
+pub fn partial_state_advance<E: EthSpec>(
+    state: &mut BeaconState<E>,
     state_root_opt: Option<Hash256>,
     target_slot: Slot,
     spec: &ChainSpec,