v2.1: Extract client code in send_transaction_service into a new structure (backport of #3423)

send-transaction-service/Cargo.toml

@@ -11,6 +11,7 @@ edition = { workspace = true }
 
 [dependencies]
 crossbeam-channel = { workspace = true }
+itertools = { workspace = true }
 log = { workspace = true }
 solana-client = { workspace = true }
 solana-connection-cache = { workspace = true }

send-transaction-service/src/lib.rs

@@ -1,6 +1,12 @@
 #![allow(clippy::arithmetic_side_effects)]
 pub mod send_transaction_service;
+pub mod send_transaction_service_stats;
 pub mod tpu_info;
+pub mod transaction_client;
+pub use {
+    send_transaction_service_stats::SendTransactionServiceStats,
+    transaction_client::{CurrentLeaderInfo, LEADER_INFO_REFRESH_RATE_MS},
+};
 
 #[macro_use]
 extern crate solana_metrics;