community: Add Sambanova Cloud Chat model community integration (#26333)

**Description:** : Add SambaNova Cloud Chat model community integration
Includes 
- chat model integration (following Standardize ChatModel docstrings)
-  tests
- docs usage notebook (following Standardize ChatModel integration docs)

https://cloud.sambanova.ai/

---------

Co-authored-by: luisfucros <luisfucros@gmail.com>
Co-authored-by: ccurme <chester.curme@gmail.com>

libs/community/tests/integration_tests/chat_models/test_sambanova.py

@@ -0,0 +1,11 @@
+from langchain_core.messages import AIMessage, HumanMessage
+
+from langchain_community.chat_models.sambanova import ChatSambaNovaCloud
+
+
+def test_chat_sambanova_cloud() -> None:
+    chat = ChatSambaNovaCloud()
+    message = HumanMessage(content="Hello")
+    response = chat.invoke([message])
+    assert isinstance(response, AIMessage)
+    assert isinstance(response.content, str)