Speed up snapshoting

Config can be fairly big, no need to deep clone it frequently

crates/rust-analyzer/src/main_loop.rs

@@ -609,7 +609,7 @@ impl GlobalState {
                                 if let Some(json) = configs.get_mut(0) {
                                     // Note that json can be null according to the spec if the client can't
                                     // provide a configuration. This is handled in Config::update below.
-                                    let mut config = this.config.clone();
+                                    let mut config = Config::clone(&*this.config);
                                     config.update(json.take());
                                     this.update_configuration(config);
                                 }