Compute recent lightclient updates (#4969)

* Compute recent lightclient updates

* Review PR

* Merge remote-tracking branch 'upstream/unstable' into lc-prod-recent-updates

* Review PR

* consistent naming

* add metrics

* revert dropping reprocessing queue

* Update light client optimistic update re-processing logic. (#7)

* Add light client server simulator tests. Co-authored by @dapplion.

* Merge branch 'unstable' into fork/dapplion/lc-prod-recent-updates

* Fix lint

* Enable light client server in simulator test.

* Fix test for light client optimistic updates and finality updates.

consensus/types/src/beacon_state.rs

@@ -1866,6 +1866,7 @@ impl<T: EthSpec> BeaconState<T> {
         };
 
         // 2. Get all `BeaconState` leaves.
+        self.initialize_tree_hash_cache();
         let mut cache = self
             .tree_hash_cache_mut()
             .take()

consensus/types/src/light_client_bootstrap.rs

@@ -9,7 +9,7 @@ use ssz_derive::{Decode, Encode};
 use std::sync::Arc;
 use test_random_derive::TestRandom;
 
-/// A LightClientBootstrap is the initializer we send over to lightclient nodes
+/// A LightClientBootstrap is the initializer we send over to light_client nodes
 /// that are trying to generate their basic storage when booting up.
 #[derive(
     Debug,

consensus/types/src/light_client_finality_update.rs

@@ -11,7 +11,7 @@ use ssz_derive::{Decode, Encode};
 use test_random_derive::TestRandom;
 use tree_hash::TreeHash;
 
-/// A LightClientFinalityUpdate is the update lightclient request or received by a gossip that
+/// A LightClientFinalityUpdate is the update light_client request or received by a gossip that
 /// signal a new finalized beacon block header for the light client sync protocol.
 #[derive(
     Debug,