Persist light client updates (#5545)

* persist light client updates

* update beacon chain to serve light client updates

* resolve todos

* cache best update

* extend cache parts

* is better light client update

* resolve merge conflict

* initial api changes

* add lc update db column

* fmt

* added tests

* add sim

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates

* fix some weird issues with the simulator

* tests

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates

* test changes

* merge conflict

* testing

* started work on ef tests and some code clean up

* update tests

* linting

* noop pre altair, were still failing on electra though

* allow for zeroed light client header

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into persist-light-client-updates

* merge unstable

* remove unwraps

* remove unwraps

* Update light_client_update.rs

* merge unstable

* move functionality to helper methods

* refactor is best update fn

* refactor is best update fn

* improve organization of light client server cache logic

* fork diget calc, and only spawn as many blcoks as we need for the lc update test

* fetch lc update from the cache if it exists

* fmt

* Fix beacon_chain tests

* Add debug code to update ranking_order ef test

* Fix compare code

* merge conflicts

* fix test

* Merge branch 'persist-light-client-updates' of https://github.com/eserilev/lighthouse into persist-light-client-updates

* Use blinded blocks for light client proofs

* fix ef test

* merge conflicts

* fix lc update check

* Lint

* resolve merge conflict

* Merge branch 'persist-light-client-updates' of https://github.com/eserilev/lighthouse into persist-light-client-updates

* revert basic sim

* small fix

* revert sim

* Review PR

* resolve merge conflicts

* Merge branch 'unstable' into persist-light-client-updates

beacon_node/store/src/leveldb_store.rs

@@ -182,7 +182,6 @@ impl<E: EthSpec> KeyValueStore<E> for LevelDB<E> {
 
     fn iter_column_from<K: Key>(&self, column: DBColumn, from: &[u8]) -> ColumnIter<K> {
         let start_key = BytesKey::from_vec(get_key_for_col(column.into(), from));
-
         let iter = self.db.iter(self.read_options());
         iter.seek(&start_key);
 

beacon_node/store/src/lib.rs

@@ -300,6 +300,9 @@ pub enum DBColumn {
     BeaconHistoricalSummaries,
     #[strum(serialize = "olc")]
     OverflowLRUCache,
+    /// For persisting eagerly computed light client data
+    #[strum(serialize = "lcu")]
+    LightClientUpdate,
 }
 
 /// A block from the database, which might have an execution payload or not.
@@ -342,7 +345,8 @@ impl DBColumn {
             | Self::BeaconStateRoots
             | Self::BeaconHistoricalRoots
             | Self::BeaconHistoricalSummaries
-            | Self::BeaconRandaoMixes => 8,
+            | Self::BeaconRandaoMixes
+            | Self::LightClientUpdate => 8,
             Self::BeaconDataColumn => DATA_COLUMN_DB_KEY_SIZE,
         }
     }