Hierarchical state diffs in hot DB (#6750)

This PR implements https://github.com/sigp/lighthouse/pull/5978 (tree-states) but on the hot DB. It allows Lighthouse to massively reduce its disk footprint during non-finality and overall I/O in all cases.

Closes https://github.com/sigp/lighthouse/issues/6580

Conga into https://github.com/sigp/lighthouse/pull/6744

### TODOs

- [x] Fix OOM in CI https://github.com/sigp/lighthouse/pull/7176
- [x] optimise store_hot_state to avoid storing a duplicate state if the summary already exists (should be safe from races now that pruning is cleaner)
- [x] mispelled: get_ancenstor_state_root
- [x] get_ancestor_state_root should use state summaries
- [x] Prevent split from changing during ancestor calc
- [x] Use same hierarchy for hot and cold

### TODO Good optimization for future PRs

- [ ] On the migration, if the latest hot snapshot is aligned with the cold snapshot migrate the diffs instead of the full states.
```
align slot  time
10485760    Nov-26-2024
12582912    Sep-14-2025
14680064    Jul-02-2026
```

### TODO Maybe things good to have

- [ ] Rename anchor_slot https://github.com/sigp/lighthouse/compare/tree-states-hot-rebase-oom...dapplion:lighthouse:tree-states-hot-anchor-slot-rename?expand=1
- [ ] Make anchor fields not public such that they must be mutated through a method. To prevent un-wanted changes of the anchor_slot

### NOTTODO

- [ ] Use fork-choice and a new method [`descendants_of_checkpoint`](ca2388e196 (diff-046fbdb517ca16b80e4464c2c824cf001a74a0a94ac0065e635768ac391062a8)) to filter only the state summaries that descend of finalized checkpoint]

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -124,7 +124,7 @@ use std::time::Duration;
 use store::iter::{BlockRootsIterator, ParentRootBlockIterator, StateRootsIterator};
 use store::{
     BlobSidecarListFromRoot, DatabaseBlock, Error as DBError, HotColdDB, HotStateSummary,
-    KeyValueStore, KeyValueStoreOp, StoreItem, StoreOp,
+    KeyValueStoreOp, StoreItem, StoreOp,
 };
 use task_executor::{ShutdownReason, TaskExecutor};
 use tokio_stream::Stream;
@@ -4043,8 +4043,6 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         ops.push(StoreOp::PutBlock(block_root, signed_block.clone()));
         ops.push(StoreOp::PutState(block.state_root(), &state));
 
-        let txn_lock = self.store.hot_db.begin_rw_transaction();
-
         if let Err(e) = self.store.do_atomically_with_block_and_blobs_cache(ops) {
             error!(
                 msg = "Restoring fork choice from disk",
@@ -4056,7 +4054,6 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 .err()
                 .unwrap_or(e.into()));
         }
-        drop(txn_lock);
 
         // The fork choice write-lock is dropped *after* the on-disk database has been updated.
         // This prevents inconsistency between the two at the expense of concurrency.
@@ -6851,13 +6848,22 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     #[allow(clippy::type_complexity)]
     pub fn chain_dump(
         &self,
+    ) -> Result<Vec<BeaconSnapshot<T::EthSpec, BlindedPayload<T::EthSpec>>>, Error> {
+        self.chain_dump_from_slot(Slot::new(0))
+    }
+
+    /// As for `chain_dump` but dumping only the portion of the chain newer than `from_slot`.
+    #[allow(clippy::type_complexity)]
+    pub fn chain_dump_from_slot(
+        &self,
+        from_slot: Slot,
     ) -> Result<Vec<BeaconSnapshot<T::EthSpec, BlindedPayload<T::EthSpec>>>, Error> {
         let mut dump = vec![];
 
         let mut prev_block_root = None;
         let mut prev_beacon_state = None;
 
-        for res in self.forwards_iter_block_roots(Slot::new(0))? {
+        for res in self.forwards_iter_block_roots(from_slot)? {
             let (beacon_block_root, _) = res?;
 
             // Do not include snapshots at skipped slots.