deprecate `get_client` and `get_multi_client` (#177)

deprecate get_client and get_multi_client

dos/src/main.rs

@@ -39,6 +39,7 @@
 //! ```
 //!
 #![allow(clippy::arithmetic_side_effects)]
+#![allow(deprecated)]
 use {
     crossbeam_channel::{select, tick, unbounded, Receiver, Sender},
     itertools::Itertools,

gossip/src/gossip_service.rs

@@ -194,6 +194,7 @@ pub fn discover(
 }
 
 /// Creates a ThinClient by selecting a valid node at random
+#[deprecated(since = "1.18.0", note = "Interface will change")]
 pub fn get_client(
     nodes: &[ContactInfo],
     socket_addr_space: &SocketAddrSpace,
@@ -209,6 +210,7 @@ pub fn get_client(
     ThinClient::new(rpc, tpu, connection_cache)
 }
 
+#[deprecated(since = "1.18.0", note = "Will be removed in favor of get_client")]
 pub fn get_multi_client(
     nodes: &[ContactInfo],
     socket_addr_space: &SocketAddrSpace,