community: Add Naver chat model & embeddings (#25162)

Reopened as a personal repo outside the organization.

## Description
- Naver HyperCLOVA X community package 
  - Add chat model & embeddings
  - Add unit test & integration test
  - Add chat model & embeddings docs
- I changed partner
package(https://github.com/langchain-ai/langchain/pull/24252) to
community package on this PR
- Could this
embeddings(https://github.com/langchain-ai/langchain/pull/21890) be
deprecated? We are trying to replace it with embedding
model(**ClovaXEmbeddings**) in this PR.

Twitter handle: None. (if needed, contact with
joonha.jeon@navercorp.com)

---
you can check our previous discussion below:

> one question on namespaces - would it make sense to have these in
.clova namespaces instead of .naver?

I would like to keep it as is, unless it is essential to unify the
package name.
(ClovaX is a branding for the model, and I plan to add other models and
components. They need to be managed as separate classes.)

> also, could you clarify the difference between ClovaEmbeddings and
ClovaXEmbeddings?

There are 3 models that are being serviced by embedding, and all are
supported in the current PR. In addition, all the functionality of CLOVA
Studio that serves actual models, such as distinguishing between test
apps and service apps, is supported. The existing PR does not support
this content because it is hard-coded.

---------

Co-authored-by: Erick Friis <erick@langchain.dev>
Co-authored-by: Vadym Barda <vadym@langchain.dev>

libs/community/langchain_community/embeddings/clova.py

@@ -3,11 +3,17 @@ from __future__ import annotations
 from typing import Any, Dict, List, Optional, cast
 
 import requests
+from langchain_core._api.deprecation import deprecated
 from langchain_core.embeddings import Embeddings
 from langchain_core.utils import convert_to_secret_str, get_from_dict_or_env
 from pydantic import BaseModel, ConfigDict, SecretStr, model_validator
 
 
+@deprecated(
+    since="0.3.4",
+    removal="1.0.0",
+    alternative_import="langchain_community.ClovaXEmbeddings",
+)
 class ClovaEmbeddings(BaseModel, Embeddings):
     """
     Clova's embedding service.