Add get_max_retransmit_slot/get_max_shred_insert_slot to RpcClient (#16243)

(cherry picked from commit 2a1639836a)

Co-authored-by: Michael Vines <mvines@gmail.com>

client/src/rpc_client.rs

@@ -869,6 +869,14 @@ impl RpcClient {
             })?
     }
 
+    pub fn get_max_retransmit_slot(&self) -> ClientResult<Slot> {
+        self.send(RpcRequest::GetMaxRetransmitSlot, Value::Null)
+    }
+
+    pub fn get_max_shred_insert_slot(&self) -> ClientResult<Slot> {
+        self.send(RpcRequest::GetMaxShredInsertSlot, Value::Null)
+    }
+
     pub fn get_multiple_accounts(&self, pubkeys: &[Pubkey]) -> ClientResult<Vec<Option<Account>>> {
         Ok(self
             .get_multiple_accounts_with_commitment(pubkeys, self.commitment_config)?