community[patch]: update copy of metadata in rockset vectorstore integration (#17612)

- **Description:** This fixes an issue with working with RecordManager.
RecordManager was generating new hashes on documents because `add_texts`
was modifying the metadata directly. Additionally moved some tests to
unit tests since that was a more appropriate home.
- **Issue:** N/A
- **Dependencies:** N/A
- **Twitter handle:** `@_morgan_adams_`

libs/community/langchain_community/vectorstores/rocksetdb.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import logging
+from copy import deepcopy
 from enum import Enum
 from typing import Any, Iterable, List, Optional, Tuple
 
@@ -123,7 +124,7 @@ class Rockset(VectorStore):
                 batch = []
             doc = {}
             if metadatas and len(metadatas) > i:
-                doc = metadatas[i]
+                doc = deepcopy(metadatas[i])
             if ids and len(ids) > i:
                 doc["_id"] = ids[i]
             doc[self._text_key] = text