async_hooks: don't read resource if ALS is disabled

Only call executionAsyncResource() in getStore() if the ALS instance is
enabled because the resource is not needed otherwise.

PR-URL: https://github.com/nodejs/node/pull/34617
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/async_hooks.js

@@ -313,8 +313,8 @@ class AsyncLocalStorage {
   }
 
   getStore() {
-    const resource = executionAsyncResource();
     if (this.enabled) {
+      const resource = executionAsyncResource();
       return resource[this.kResourceStore];
     }
   }