Compute a "proper" hash in the AnnotationStorage.prototype.modifiedIds getter

Currently the hash-property is just a stringified Array, which means that the hash-property can become arbitrarily long. That's not a good idea since it's used to compute a cache-key, in the API, which is then sent to the worker-thread. Hence the hash-property should be reasonably short, and its length should *not* depend on the number of modified editors, which can be achieved by using `MurmurHash3_64` here as well.

src/display/annotation_storage.js

@@ -303,9 +303,15 @@ class AnnotationStorage {
         ids.push(value.annotationElementId);
       }
     }
+    let hash = "";
+    if (ids.length) {
+      const h = new MurmurHash3_64();
+      h.update(ids.join(","));
+      hash = h.hexdigest();
+    }
     return (this.#modifiedIds = {
       ids: new Set(ids),
-      hash: ids.join(","),
+      hash,
     });
   }