Add a client for BankForks (#10728)

Also:
* Use BanksClient in solana-tokens

cli-config/src/config.rs

@@ -76,6 +76,17 @@ impl Config {
         ws_url.to_string()
     }
 
+    pub fn compute_rpc_banks_url(json_rpc_url: &str) -> String {
+        let json_rpc_url: Option<Url> = json_rpc_url.parse().ok();
+        if json_rpc_url.is_none() {
+            return "".to_string();
+        }
+        let mut url = json_rpc_url.unwrap();
+        let port = url.port_or_known_default().unwrap_or(80);
+        url.set_port(Some(port + 2)).expect("unable to set port");
+        url.to_string()
+    }
+
     pub fn import_address_labels<P>(&mut self, filename: P) -> Result<(), io::Error>
     where
         P: AsRef<Path>,
@@ -122,4 +133,28 @@ mod test {
 
         assert_eq!(Config::compute_websocket_url(&"garbage"), String::new());
     }
+
+    #[test]
+    fn compute_rpc_banks_url() {
+        assert_eq!(
+            Config::compute_rpc_banks_url(&"http://devnet.solana.com"),
+            "http://devnet.solana.com:82/".to_string()
+        );
+
+        assert_eq!(
+            Config::compute_rpc_banks_url(&"https://devnet.solana.com"),
+            "https://devnet.solana.com:445/".to_string()
+        );
+
+        assert_eq!(
+            Config::compute_rpc_banks_url(&"http://example.com:8899"),
+            "http://example.com:8901/".to_string()
+        );
+        assert_eq!(
+            Config::compute_rpc_banks_url(&"https://example.com:1234"),
+            "https://example.com:1236/".to_string()
+        );
+
+        assert_eq!(Config::compute_rpc_banks_url(&"garbage"), String::new());
+    }
 }