Remove state lru cache (#8724)

N/A


  In https://github.com/sigp/lighthouse/pull/4801 , we added a state lru cache to avoid having too many states in memory which was a concern with 200mb+ states pre tree-states.
With https://github.com/sigp/lighthouse/pull/5891 , we made the overflow cache a simpler in memory lru cache that can only hold 32 pending states at the most and doesn't flush anything to disk. As noted in #5891, we can always fetch older blocks which never became available over rpc if they become available later.

Since we merged tree states, I don't think the state lru cache is relevant anymore. Instead of having the `DietAvailabilityPendingExecutedBlock` that stores only the state root, we can just store the full state in the `AvailabilityPendingExecutedBlock`.
Given entries in the cache can span max 1 epoch (cache size is 32), the underlying `BeaconState` objects in the cache share most of their memory. The state_lru_cache is one level of indirection that doesn't give us any benefit.
Please check me on this cc @dapplion


Co-Authored-By: Pawan Dhananjay <pawandhananjay@gmail.com>

beacon_node/beacon_chain/src/test_utils.rs

@@ -222,7 +222,6 @@ pub fn test_da_checker<E: EthSpec>(
         Duration::from_secs(spec.seconds_per_slot),
     );
     let kzg = get_kzg(&spec);
-    let store = Arc::new(HotColdDB::open_ephemeral(<_>::default(), spec.clone()).unwrap());
     let ordered_custody_column_indices = generate_data_column_indices_rand_order::<E>();
     let custody_context = Arc::new(CustodyContext::new(
         node_custody_type,
@@ -234,7 +233,6 @@ pub fn test_da_checker<E: EthSpec>(
         complete_blob_backfill,
         slot_clock,
         kzg,
-        store,
         custody_context,
         spec,
     )