docs, templates: update schema imports to core (#17885)

- chat models, messages
- documents
- agentaction/finish
- baseretriever,document
- stroutputparser
- more messages
- basemessage
- format_document
- baseoutputparser

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

templates/self-query-qdrant/self_query_qdrant/helper.py

@@ -1,7 +1,7 @@
 from string import Formatter
 from typing import List
 
-from langchain.schema import Document
+from langchain_core.documents import Document
 
 document_template = """
 PASSAGE: {page_content}