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/store/src/database/leveldb_impl.rs

@@ -13,7 +13,6 @@ use leveldb::{
     iterator::{Iterable, LevelDBIterator},
     options::{Options, ReadOptions},
 };
-use parking_lot::{Mutex, MutexGuard};
 use std::collections::HashSet;
 use std::marker::PhantomData;
 use std::path::Path;
@@ -23,8 +22,6 @@ use super::interface::WriteOptions;
 
 pub struct LevelDB<E: EthSpec> {
     db: Database<BytesKey>,
-    /// A mutex to synchronise sensitive read-write transactions.
-    transaction_mutex: Mutex<()>,
     _phantom: PhantomData<E>,
 }
 
@@ -43,11 +40,9 @@ impl<E: EthSpec> LevelDB<E> {
         options.create_if_missing = true;
 
         let db = Database::open(path, options)?;
-        let transaction_mutex = Mutex::new(());
 
         Ok(Self {
             db,
-            transaction_mutex,
             _phantom: PhantomData,
         })
     }
@@ -177,10 +172,6 @@ impl<E: EthSpec> LevelDB<E> {
         Ok(())
     }
 
-    pub fn begin_rw_transaction(&self) -> MutexGuard<()> {
-        self.transaction_mutex.lock()
-    }
-
     /// Compact all values in the states and states flag columns.
     pub fn compact(&self) -> Result<(), Error> {
         let _timer = metrics::start_timer(&metrics::DISK_DB_COMPACT_TIMES);