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

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

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

templates/xml-agent/xml_agent/agent.py

@@ -2,10 +2,10 @@ from typing import List, Tuple
 
 from langchain.agents import AgentExecutor
 from langchain.agents.format_scratchpad import format_xml
-from langchain.schema import AIMessage, HumanMessage
 from langchain.tools import DuckDuckGoSearchRun
 from langchain.tools.render import render_text_description
 from langchain_community.chat_models import ChatAnthropic
+from langchain_core.messages import AIMessage, HumanMessage
 from langchain_core.pydantic_v1 import BaseModel, Field
 
 from xml_agent.prompts import conversational_prompt, parse_output