Manual finalization endpoint (#7059)

* Load block roots from fork choice where possible to avoid loading state from disk when serving block by range requests.

* Check if the start slot is newer than finalization (`start_slot >= finalized_slot`), and use fork choice in that case.

* force finalization endpoint

* cleanup

* Remove ds store

* Don't import blocks that conflict with the split

* Disconnect and ban peer if we get blocks conflicting manual checkpoint

* immediately commit state to cold db

* revert

* Fix descent from split check

* Add safety check to checkpoint when doing manual finalization.

---------

Co-authored-by: Jimmy Chen <jchen.tc@gmail.com>
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
Co-authored-by: Pawan Dhananjay <pawandhananjay@gmail.com>

beacon_node/network/src/network_beacon_processor/sync_methods.rs

@@ -740,6 +740,19 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
                 debug!(self.log, "Finalized or earlier block processed";);
                 Ok(())
             }
+            BlockError::NotFinalizedDescendant { block_parent_root } => {
+                debug!(
+                    self.log,
+                    "Not syncing to a chain that conflicts with the canonical or manual finalized checkpoint"
+                );
+                Err(ChainSegmentFailed {
+                    message: format!(
+                        "Block with parent_root {} conflicts with our checkpoint state",
+                        block_parent_root
+                    ),
+                    peer_action: Some(PeerAction::Fatal),
+                })
+            }
             BlockError::GenesisBlock => {
                 debug!(self.log, "Genesis block was processed");
                 Ok(())