Reduce duplication for reference tests with an annotationStorage entry

Currently we duplicate the same code more than once in the `test/driver.js` file, which we can avoid by adding a new `AnnotationStorage` helper method instead.

src/display/annotation_storage.js

@@ -120,10 +120,22 @@ class AnnotationStorage {
     return this.#storage.has(key);
   }
 
+  /**
+   * @returns {Object | null}
+   */
   getAll() {
     return this.#storage.size > 0 ? objectFromMap(this.#storage) : null;
   }
 
+  /**
+   * @param {Object} obj
+   */
+  setAll(obj) {
+    for (const [key, val] of Object.entries(obj)) {
+      this.setValue(key, val);
+    }
+  }
+
   get size() {
     return this.#storage.size;
   }