Introduce `assistant.execute_tools = true/false` option to replace the `auto_tool_execution` parameter.

[andreibondarev]

Description

In order to make the Assistant's DSL more intuitive we should rename the auto_tool_execution: parameter to execute_tools:. This is also in line with the openai/swarm agent framework.

We should be able to set this option at the Assistant-level and not have to specify it every time. You should still be able to override this setting when you're explicitly calling the method with .run(execute_tools: false).

assistant = Langchain::Assistant.new(
  llm: llm,
  execute_tools: true
)

assistant.add_message(content: "...")

assistant.run(execute_tools: false)

Tasks

• [ ] Rename auto_tool_execution: option to execute_tools:
• [ ] Allow setting assistant.execute_tools and default it to true.
• [ ] Allow overriding assistant.execute_tools when calling assistant.run(execute_tools:)