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.

beacon_node/http_api/src/lib.rs

@@ -2434,9 +2434,8 @@ pub fn serve<T: BeaconChainTypes>(
              accept_header: Option<api_types::Accept>| {
                 task_spawner.blocking_response_task(Priority::P1, move || {
                     let update = chain
-                        .latest_seen_optimistic_update
-                        .lock()
-                        .clone()
+                        .light_client_server_cache
+                        .get_latest_optimistic_update()
                         .ok_or_else(|| {
                             warp_utils::reject::custom_not_found(
                                 "No LightClientOptimisticUpdate is available".to_string(),
@@ -2482,9 +2481,8 @@ pub fn serve<T: BeaconChainTypes>(
              accept_header: Option<api_types::Accept>| {
                 task_spawner.blocking_response_task(Priority::P1, move || {
                     let update = chain
-                        .latest_seen_finality_update
-                        .lock()
-                        .clone()
+                        .light_client_server_cache
+                        .get_latest_finality_update()
                         .ok_or_else(|| {
                             warp_utils::reject::custom_not_found(
                                 "No LightClientFinalityUpdate is available".to_string(),