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/beacon_chain/src/errors.rs

@@ -61,6 +61,7 @@ pub enum BeaconChainError {
     ForkChoiceStoreError(ForkChoiceStoreError),
     MissingBeaconBlock(Hash256),
     MissingBeaconState(Hash256),
+    MissingHotStateSummary(Hash256),
     SlotProcessingError(SlotProcessingError),
     EpochProcessingError(EpochProcessingError),
     StateAdvanceError(StateAdvanceError),
@@ -181,9 +182,9 @@ pub enum BeaconChainError {
         execution_block_hash: Option<ExecutionBlockHash>,
     },
     ForkchoiceUpdate(execution_layer::Error),
-    FinalizedCheckpointMismatch {
-        head_state: Checkpoint,
-        fork_choice: Hash256,
+    InvalidCheckpoint {
+        state_root: Hash256,
+        checkpoint: Checkpoint,
     },
     InvalidSlot(Slot),
     HeadBlockNotFullyVerified {