Separated llms from the main llm.py file and fixed some deprication bugs

examples/lightrag_oracle_demo.py

@@ -3,7 +3,7 @@ import os
 from pathlib import Path
 import asyncio
 from lightrag import LightRAG, QueryParam
-from lightrag.llm import openai_complete_if_cache, openai_embedding
+from lightrag.llm.openai import openai_complete_if_cache, openai_embed
 from lightrag.utils import EmbeddingFunc
 import numpy as np
 from lightrag.kg.oracle_impl import OracleDB
@@ -42,7 +42,7 @@ async def llm_model_func(
 
 
 async def embedding_func(texts: list[str]) -> np.ndarray:
-    return await openai_embedding(
+    return await openai_embed(
         texts,
         model=EMBEDMODEL,
         api_key=APIKEY,