Fix CGC backfill race condition (#8267)

During custody backfill sync there could be an edge case where we update CGC at the same time where we are importing a batch of columns which may cause us to incorrectly overwrite values when calling `backfill_validator_custody_requirements`. To prevent this race condition, the expected cgc is now passed into this function and is used to check if the expected cgc == the current validator cgc. If the values arent equal, this probably indicates that a very recent CGC occurred so we do not prune/update values in the `epoch_validator_custody_requirements` map.


  


Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

beacon_node/network/src/sync/custody_backfill_sync/mod.rs

@@ -504,6 +504,7 @@ impl<T: BeaconChainTypes> CustodyBackFillSync<T> {
                 run_id: self.run_id,
             },
             data_columns,
+            self.cgc,
         ) {
             crit!(
                 msg = "process_batch",