Add distributed flag to VC to enable support for DVT (#4867)

* Initial flag building

* Update validator_client/src/cli.rs

Co-authored-by: Abhishek Kumar <43061995+xenowits@users.noreply.github.com>

* Merge latest unstable

* Per slot aggregates

* One slot lookahead for sync committee aggregates

* Update validator_client/src/duties_service.rs

Co-authored-by: Abhishek Kumar <43061995+xenowits@users.noreply.github.com>

* Rename selection_look_ahead

* Merge branch 'unstable' into vc-distributed

* Merge remote-tracking branch 'origin/unstable' into vc-distributed

* Update CLI text

validator_client/src/lib.rs

@@ -39,7 +39,7 @@ use account_utils::validator_definitions::ValidatorDefinitions;
 use attestation_service::{AttestationService, AttestationServiceBuilder};
 use block_service::{BlockService, BlockServiceBuilder};
 use clap::ArgMatches;
-use duties_service::DutiesService;
+use duties_service::{sync::SyncDutiesMap, DutiesService};
 use environment::RuntimeContext;
 use eth2::{reqwest::ClientBuilder, types::Graffiti, BeaconNodeHttpClient, StatusCode, Timeouts};
 use http_api::ApiSecret;
@@ -451,13 +451,14 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
         let duties_service = Arc::new(DutiesService {
             attesters: <_>::default(),
             proposers: <_>::default(),
-            sync_duties: <_>::default(),
+            sync_duties: SyncDutiesMap::new(config.distributed),
             slot_clock: slot_clock.clone(),
             beacon_nodes: beacon_nodes.clone(),
             validator_store: validator_store.clone(),
             spec: context.eth2_config.spec.clone(),
             context: duties_context,
             enable_high_validator_count_metrics: config.enable_high_validator_count_metrics,
+            distributed: config.distributed,
         });
 
         // Update the metrics server.