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/block_verification.rs

@@ -90,7 +90,7 @@ use std::fmt::Debug;
 use std::fs;
 use std::io::Write;
 use std::sync::Arc;
-use store::{Error as DBError, HotStateSummary, KeyValueStore, StoreOp};
+use store::{Error as DBError, KeyValueStore};
 use strum::AsRefStr;
 use task_executor::JoinHandle;
 use tracing::{debug, error};
@@ -1467,28 +1467,19 @@ impl<T: BeaconChainTypes> ExecutionPendingBlock<T> {
                 // processing, but we get early access to it.
                 let state_root = state.update_tree_hash_cache()?;
 
-                // Store the state immediately.
-                let txn_lock = chain.store.hot_db.begin_rw_transaction();
+                // Store the state immediately. States are ONLY deleted on finalization pruning, so
+                // we won't have race conditions where we should have written a state and didn't.
                 let state_already_exists =
                     chain.store.load_hot_state_summary(&state_root)?.is_some();
 
-                let state_batch = if state_already_exists {
+                if state_already_exists {
                     // If the state exists, we do not need to re-write it.
-                    vec![]
                 } else {
-                    vec![if state.slot() % T::EthSpec::slots_per_epoch() == 0 {
-                        StoreOp::PutState(state_root, &state)
-                    } else {
-                        StoreOp::PutStateSummary(
-                            state_root,
-                            HotStateSummary::new(&state_root, &state)?,
-                        )
-                    }]
+                    // Recycle store codepath to create a state summary and store the state / diff
+                    let mut ops = vec![];
+                    chain.store.store_hot_state(&state_root, &state, &mut ops)?;
+                    chain.store.hot_db.do_atomically(ops)?;
                 };
-                chain
-                    .store
-                    .do_atomically_with_block_and_blobs_cache(state_batch)?;
-                drop(txn_lock);
 
                 state_root
             };