Refactor RPC subscriptions account handling (#9888)

* Switch subscriptions to use commitment instead of confirmations

* Add bank method to return account and last-modified slot

* Add last_modified_slot to subscription data and use to filter account subscriptions

* Update tests to non-zero last_notified_slot

* Add accounts subscriptions to test; fails at higher tx load

* Pass BankForks to RpcSubscriptions

* Use BankForks on add_account_subscription to properly initialize last_notified_slot

* Bundle subscriptions

* Check for non-equality

* Use commitment to initialize last_notified_slot; revert context.slot chage

core/src/validator.rs

@@ -241,7 +241,11 @@ impl Validator {
             BlockCommitmentCache::default_with_blockstore(blockstore.clone()),
         ));
 
-        let subscriptions = Arc::new(RpcSubscriptions::new(&exit, block_commitment_cache.clone()));
+        let subscriptions = Arc::new(RpcSubscriptions::new(
+            &exit,
+            bank_forks.clone(),
+            block_commitment_cache.clone(),
+        ));
 
         let rpc_service = config.rpc_ports.map(|(rpc_port, rpc_pubsub_port)| {
             if ContactInfo::is_valid_address(&node.info.rpc) {