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/fork_choice/src/fork_choice_store.rs

@@ -19,7 +19,7 @@ use types::{AbstractExecPayload, BeaconBlockRef, BeaconState, Checkpoint, EthSpe
 /// The primary motivation for defining this as a trait to be implemented upstream rather than a
 /// concrete struct is to allow this crate to be free from "impure" on-disk database logic,
 /// hopefully making auditing easier.
-pub trait ForkChoiceStore<T: EthSpec>: Sized {
+pub trait ForkChoiceStore<E: EthSpec>: Sized {
     type Error: Debug;
 
     /// Returns the last value passed to `Self::set_current_slot`.
@@ -34,11 +34,11 @@ pub trait ForkChoiceStore<T: EthSpec>: Sized {
 
     /// Called whenever `ForkChoice::on_block` has verified a block, but not yet added it to fork
     /// choice. Allows the implementer to performing caching or other housekeeping duties.
-    fn on_verified_block<Payload: AbstractExecPayload<T>>(
+    fn on_verified_block<Payload: AbstractExecPayload<E>>(
         &mut self,
-        block: BeaconBlockRef<T, Payload>,
+        block: BeaconBlockRef<E, Payload>,
         block_root: Hash256,
-        state: &BeaconState<T>,
+        state: &BeaconState<E>,
     ) -> Result<(), Self::Error>;
 
     /// Returns the `justified_checkpoint`.