Feature Request: Support asynchronous CLI methods in CliApp

[KanchiShimono]

Currently, the CliApp.run function only supports synchronous methods. When attempting to pass an asynchronous method to CliApp.run, an error is raised indicating that the coroutine was never awaited. As asynchronous programming becomes more prevalent in Python applications, it would be extremely helpful if CliApp could handle async methods out of the box.

Background

The pydantic-settings library provides a CliApp class that allows running methods of a BaseSettings subclass as CLI commands. However, passing an async method to CliApp.run triggers a warning because the method is never awaited internally.

Sample Code

from pydantic_settings import BaseSettings, CliApp

class AsyncSettings(BaseSettings):
    async def cli_cmd(self) -> None:
        print('Hello from an async CLI method!')

Error

.../.venv/lib/python3.12/site-packages/pydantic_settings/main.py:450: RuntimeWarning: coroutine 'AsyncSettings.cli_cmd' was never awaited
  getattr(type(model), cli_cmd_method_name)(model)
RuntimeWarning: Enable tracemalloc to get the object allocation traceback