Add quic-client module (#23166)

* Add quic-client module to send transactions via quic, abstracted behind the TpuConnection trait (along with a legacy UDP implementation of TpuConnection) and change thin-client to use TpuConnection

client/src/tpu_connection.rs

@@ -0,0 +1,19 @@
+use {
+    solana_sdk::{transaction::Transaction, transport::Result as TransportResult},
+    std::net::{SocketAddr, UdpSocket},
+};
+
+pub trait TpuConnection {
+    fn new(client_socket: UdpSocket, tpu_addr: SocketAddr) -> Self;
+
+    fn tpu_addr(&self) -> &SocketAddr;
+
+    fn send_transaction(&self, tx: &Transaction) -> TransportResult<()> {
+        let data = bincode::serialize(tx).expect("serialize Transaction in send_transaction");
+        self.send_wire_transaction(data)
+    }
+
+    fn send_wire_transaction(&self, data: Vec<u8>) -> TransportResult<()>;
+
+    fn send_batch(&self, transactions: Vec<Transaction>) -> TransportResult<()>;
+}