feat: Enhanced async tool support for smolagents

[h9-tec]

• Convert GoogleSearchTool, ApiWebSearchTool, and WebSearchTool to async
• Improve async/sync detection and handling in Tool base class
• Enhanced ToolCallingAgent with better async tool execution
• Add comprehensive async support for web search tools using aiohttp
• Add more tools to TOOL_MAPPING for better discoverability
• Maintain backward compatibility with sync tool calls
• Support concurrent async tool execution for better performance

Key improvements:

• All web-based tools (search, webpage visiting) now use async HTTP requests
• Tools automatically detect if they're async and handle accordingly
• Agents seamlessly handle mixed sync/async tool execution
• Better error handling and timeout management for async operations
• Full backward compatibility - sync calls on async tools still work

[aymeric-roucher]

Thank you, will have a look! Meanwhile you'll probably need to do a (complicated) rebase on #1482 that will be merged first

[Copilot]

Pull Request Overview

This PR enhances async tool support in smolagents by converting several tools to async, improving async/sync detection, and improving error handling and performance when executing tools concurrently.

• Converted tool forward methods to async and added acall methods where needed.
• Improved handling of mixed async/sync invocations through event loop detection and thread pool execution.
• Enhanced error messaging and expanded TOOL_MAPPING for better discoverability.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/smolagents/tools.py	Added async support and a new acall method in the Tool base class.
src/smolagents/default_tools.py	Converted synchronous web search and page visit logic to async, with thread pool wrappers for blocking calls and enhanced error handling.
src/smolagents/agents.py	Updated agent execution flow to support async tool calls and consolidated async-to-sync handling logic.

Comments suppressed due to low confidence (1)

src/smolagents/agents.py:1416

• The async-to-sync handling logic via thread pool is duplicated; consider refactoring this pattern into a shared helper function to improve maintainability and reduce code duplication.

                    # We need to handle this differently - for now we'll use asyncio.run_coroutine_threadsafe

[Copilot]

Consider moving the import of 'concurrent.futures' to the module level to reduce repetitive imports and improve startup performance in call.

Suggested change

import concurrent.futures