refactor: Rename updatePartial method to mergeItemData in CollectionR…

…eference

This commit renames the `updatePartial` method to `mergeItemData` in the `CollectionReference` class. The purpose of this change is to provide a more descriptive and accurate method name that reflects the behavior of merging partial data into an existing item. This change aligns with the recent refactoring of other methods in the `CollectionReference` class, such as `remove` to `removeItem`, `append` to `appendItem`, and `add` to `addItem`. The renaming of methods improves code readability and consistency.

BREAKING CHANGE: The `updatePartial` method has been replaced with `mergeItemData` in the `CollectionReference` class. Developers should update their code to use the new method name.

packages/reference/src/collection-reference.ts

@@ -444,11 +444,11 @@ export class CollectionReference<TItem extends JsonifiableObject = JsonifiableOb
    *
    * @example
    * ```typescript
-   * collectionRef.updatePartial(itemId, partialUpdate);
+   * collectionRef.mergeItemData(itemId, partialUpdate);
    * ```
    */
-  updatePartial(itemId: string | number, data: Partial<TItem>): void {
-    this.logger__.logMethodArgs?.('updatePartial', {itemId, data});
+  mergeItemData(itemId: string | number, data: Partial<TItem>): void {
+    this.logger__.logMethodArgs?.('mergeItemData', {itemId, data});
     Object.assign(this.item__(itemId).data, data);
     this.updated__(itemId);
   }