docs, community[patch], experimental[patch], langchain[patch], cli[pa… (#15412)

…tch]: import models from community

ran
```bash
git grep -l 'from langchain\.chat_models' | xargs -L 1 sed -i '' "s/from\ langchain\.chat_models/from\ langchain_community.chat_models/g"
git grep -l 'from langchain\.llms' | xargs -L 1 sed -i '' "s/from\ langchain\.llms/from\ langchain_community.llms/g"
git grep -l 'from langchain\.embeddings' | xargs -L 1 sed -i '' "s/from\ langchain\.embeddings/from\ langchain_community.embeddings/g"
git checkout master libs/langchain/tests/unit_tests/llms
git checkout master libs/langchain/tests/unit_tests/chat_models
git checkout master libs/langchain/tests/unit_tests/embeddings/test_imports.py
make format
cd libs/langchain; make format
cd ../experimental; make format
cd ../core; make format
```

templates/rag-mongo/ingest.py

@@ -1,9 +1,9 @@
 import os
 
 from langchain.document_loaders import PyPDFLoader
-from langchain.embeddings import OpenAIEmbeddings
 from langchain.text_splitter import RecursiveCharacterTextSplitter
 from langchain.vectorstores import MongoDBAtlasVectorSearch
+from langchain_community.embeddings import OpenAIEmbeddings
 from pymongo import MongoClient
 
 MONGO_URI = os.environ["MONGO_URI"]