Implement checkpoint sync (#2244)

## Issue Addressed

Closes #1891
Closes #1784

## Proposed Changes

Implement checkpoint sync for Lighthouse, enabling it to start from a weak subjectivity checkpoint.

## Additional Info

- [x] Return unavailable status for out-of-range blocks requested by peers (#2561)
- [x] Implement sync daemon for fetching historical blocks (#2561)
- [x] Verify chain hashes (either in `historical_blocks.rs` or the calling module)
- [x] Consistency check for initial block + state
- [x] Fetch the initial state and block from a beacon node HTTP endpoint
- [x] Don't crash fetching beacon states by slot from the API
- [x] Background service for state reconstruction, triggered by CLI flag or API call.

Considered out of scope for this PR:

- Drop the requirement to provide the `--checkpoint-block` (this would require some pretty heavy refactoring of block verification)


Co-authored-by: Diva M <divma@protonmail.com>

beacon_node/http_api/tests/tests.rs

@@ -2101,6 +2101,29 @@ impl ApiTester {
         self
     }
 
+    pub async fn test_get_lighthouse_database_info(self) -> Self {
+        let info = self.client.get_lighthouse_database_info().await.unwrap();
+
+        assert_eq!(info.anchor, self.chain.store.get_anchor_info());
+        assert_eq!(info.split, self.chain.store.get_split_info());
+        assert_eq!(
+            info.schema_version,
+            store::metadata::CURRENT_SCHEMA_VERSION.as_u64()
+        );
+
+        self
+    }
+
+    pub async fn test_post_lighthouse_database_reconstruct(self) -> Self {
+        let response = self
+            .client
+            .post_lighthouse_database_reconstruct()
+            .await
+            .unwrap();
+        assert_eq!(response, "success");
+        self
+    }
+
     pub async fn test_post_lighthouse_liveness(self) -> Self {
         let epoch = self.chain.epoch().unwrap();
         let head_state = self.chain.head_beacon_state().unwrap();
@@ -2653,6 +2676,10 @@ async fn lighthouse_endpoints() {
         .await
         .test_get_lighthouse_staking()
         .await
+        .test_get_lighthouse_database_info()
+        .await
+        .test_post_lighthouse_database_reconstruct()
+        .await
         .test_post_lighthouse_liveness()
         .await;
 }