Optimize RPC pubsub for multiple clients with the same subscription (#18943)

* reimplement rpc pubsub with a broadcast queue

* update tests for new pubsub implementation

* fix: fix review suggestions

* chore(rpc): add additional pubsub metrics

* integrate max subscriptions check into SubscriptionTracker to reduce locking

* separate subscription control from tracker

* limit memory usage of items in pubsub broadcast queue, improve error handling

* add more pubsub metrics

* add final count metrics to pubsub

* add metric for total number of subscriptions

* fix small review suggestions

* remove by_params from SubscriptionTracker and add node_progress_watchers map instead

* add subscription tracker tests

* add metrics for number of pubsub notifications as a counter

* ignore clippy lint in TokenCounter

* fix underflow in token counter

* reduce queue capacity in pubsub tests

* fix(rpc): fix test timeouts

* fix race in account subscription test

* Add RpcSubscriptions::new_for_tests

Co-authored-by: Pavel Strakhov <p.strakhov@iconic.vc>
Co-authored-by: Nikita Podoliako <n.podoliako@zubr.io>
Co-authored-by: Tyera Eulberg <tyera@solana.com>

account-decoder/src/lib.rs

@@ -49,7 +49,7 @@ pub enum UiAccountData {
     Binary(String, UiAccountEncoding),
 }
 
-#[derive(Serialize, Deserialize, Clone, Copy, Debug, PartialEq)]
+#[derive(Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Eq, Hash)]
 #[serde(rename_all = "camelCase")]
 pub enum UiAccountEncoding {
     Binary, // Legacy. Retained for RPC backwards compatibility
@@ -179,7 +179,7 @@ impl Default for UiFeeCalculator {
     }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct UiDataSliceConfig {
     pub offset: usize,