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_request.rs

@@ -32,6 +32,8 @@ pub enum RpcRequest {
     GetInflationRate,
     GetLargestAccounts,
     GetLeaderSchedule,
+    GetMaxRetransmitSlot,
+    GetMaxShredInsertSlot,
     GetMinimumBalanceForRentExemption,
     GetMultipleAccounts,
     GetProgramAccounts,
@@ -91,6 +93,8 @@ impl fmt::Display for RpcRequest {
             RpcRequest::GetInflationRate => "getInflationRate",
             RpcRequest::GetLargestAccounts => "getLargestAccounts",
             RpcRequest::GetLeaderSchedule => "getLeaderSchedule",
+            RpcRequest::GetMaxRetransmitSlot => "getMaxRetransmitSlot",
+            RpcRequest::GetMaxShredInsertSlot => "getMaxShredInsertSlot",
             RpcRequest::GetMinimumBalanceForRentExemption => "getMinimumBalanceForRentExemption",
             RpcRequest::GetMultipleAccounts => "getMultipleAccounts",
             RpcRequest::GetProgramAccounts => "getProgramAccounts",