couchbase: Add chat message history (#24356)

**Description:** : Add support for chat message history using Couchbase

- [x] **Add tests and docs**: If you're adding a new integration, please
include
1. a test for the integration, preferably unit tests that do not rely on
network access,
2. an example notebook showing its use. It lives in
`docs/docs/integrations` directory.


- [x] **Lint and test**: Run `make format`, `make lint` and `make test`
from the root of the package(s) you've modified. See contribution
guidelines for more: https://python.langchain.com/docs/contributing/

---------

Co-authored-by: Nithish Raghunandanan <nithishr@users.noreply.github.com>

libs/partners/couchbase/langchain_couchbase/__init__.py

@@ -1,7 +1,10 @@
+from langchain_couchbase.cache import CouchbaseCache, CouchbaseSemanticCache
+from langchain_couchbase.chat_message_histories import CouchbaseChatMessageHistory
 from langchain_couchbase.vectorstores import CouchbaseVectorStore
 
 __all__ = [
     "CouchbaseVectorStore",
     "CouchbaseCache",
     "CouchbaseSemanticCache",
+    "CouchbaseChatMessageHistory",
 ]