Desktop: Move preferences persistence to native (#3138)

* Move preference persistence to native

* Pass preferences as struct instead of serialized to string

desktop/src/app.rs

@@ -214,6 +214,15 @@ impl WinitApp {
 					self.dispatch_desktop_wrapper_message(message);
 				}
 			}
+			DesktopFrontendMessage::PersistenceWritePreferences { preferences } => {
+				self.persistent_data.write_preferences(preferences);
+			}
+			DesktopFrontendMessage::PersistenceLoadPreferences => {
+				if let Some(preferences) = self.persistent_data.load_preferences() {
+					let message = DesktopWrapperMessage::LoadPreferences { preferences };
+					self.dispatch_desktop_wrapper_message(message);
+				}
+			}
 		}
 	}