Rpc -> proper optimistic confirmation (#12514)

* Add service to track the most recent optimistically confirmed bank

* Plumb service into ClusterInfoVoteListener and ReplayStage

* Clean up test

* Use OptimisticallyConfirmedBank in RPC

* Remove superfluous notifications from RpcSubscriptions

* Use crossbeam to avoid mpsc recv_timeout panic

* Review comments

* Remove superfluous last_checked_slots, but pass in OptimisticallyConfirmedBank for complete correctness

core/src/rpc_pubsub_service.rs

@@ -73,6 +73,7 @@ impl PubSubService {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::optimistically_confirmed_bank_tracker::OptimisticallyConfirmedBank;
     use solana_runtime::{
         bank::Bank,
         bank_forks::BankForks,
@@ -91,10 +92,13 @@ mod tests {
         let GenesisConfigInfo { genesis_config, .. } = create_genesis_config(10_000);
         let bank = Bank::new(&genesis_config);
         let bank_forks = Arc::new(RwLock::new(BankForks::new(bank)));
+        let optimistically_confirmed_bank =
+            OptimisticallyConfirmedBank::locked_from_bank_forks_root(&bank_forks);
         let subscriptions = Arc::new(RpcSubscriptions::new(
             &exit,
             bank_forks,
             Arc::new(RwLock::new(BlockCommitmentCache::new_for_tests())),
+            optimistically_confirmed_bank,
         ));
         let pubsub_service = PubSubService::new(&subscriptions, pubsub_addr, &exit);
         let thread = pubsub_service.thread_hdl.thread();