feat(connector): allow clients to specify the x224 nego request data (#580)

The previous code would (correctly) set a cookie containining the
username, but only when using username/password credentials. When
smart card credentials are used, the cookie would always contain
the empty string.

crates/ironrdp/examples/screenshot.rs

@@ -223,6 +223,7 @@ fn build_config(username: String, password: String, domain: Option<String>) -> c
 
         // Disable custom pointers (there is no user interaction anyway)
         no_server_pointer: true,
+        request_data: None,
         autologon: false,
         pointer_software_rendering: true,
         performance_flags: PerformanceFlags::default(),