Implement /lighthouse/custody/info API (#8276)

Closes:

- https://github.com/sigp/lighthouse/issues/8249


  New `/lighthouse/custody` API including:

- [x] Earliest custodied data column slot
- [x] Node CGC
- [x] Custodied columns


Co-Authored-By: Michael Sproul <michael@sigmaprime.io>

beacon_node/http_api/src/lib.rs

@@ -13,6 +13,7 @@ mod block_packing_efficiency;
 mod block_rewards;
 mod build_block_contents;
 mod builder_states;
+mod custody;
 mod database;
 mod light_client;
 mod metrics;
@@ -4590,6 +4591,19 @@ pub fn serve<T: BeaconChainTypes>(
             },
         );
 
+    // GET lighthouse/custody/info
+    let get_lighthouse_custody_info = warp::path("lighthouse")
+        .and(warp::path("custody"))
+        .and(warp::path("info"))
+        .and(warp::path::end())
+        .and(task_spawner_filter.clone())
+        .and(chain_filter.clone())
+        .then(
+            |task_spawner: TaskSpawner<T::EthSpec>, chain: Arc<BeaconChain<T>>| {
+                task_spawner.blocking_json_task(Priority::P1, move || custody::info(chain))
+            },
+        );
+
     // GET lighthouse/analysis/block_rewards
     let get_lighthouse_block_rewards = warp::path("lighthouse")
         .and(warp::path("analysis"))
@@ -4891,6 +4905,7 @@ pub fn serve<T: BeaconChainTypes>(
                 .uor(get_lighthouse_validator_inclusion)
                 .uor(get_lighthouse_staking)
                 .uor(get_lighthouse_database_info)
+                .uor(get_lighthouse_custody_info)
                 .uor(get_lighthouse_block_rewards)
                 .uor(get_lighthouse_attestation_performance)
                 .uor(get_beacon_light_client_optimistic_update)