Use AsyncLLM for CodeActAgent and other components

[tofarr]

This PR updates the CodeActAgent class to use the async variant of LLM completion, which should improve performance by avoiding blocking operations. The changes have been made in a way that maintains backward compatibility with existing code while enabling async operations.

Changes:

• Update CodeActAgent to use AsyncLLM and async step method
• Update base Agent class to make step method async
• Update all other agent implementations to use async step:
  • VisualBrowsingAgent
  • BrowsingAgent
  • DummyAgent
  • DelegatorAgent
  • MicroAgent
• Update LLM-based condensers to use AsyncLLM and async_completion
• Update InvariantAnalyzer to use AsyncLLM and async_completion
• Update FileEditRuntimeMixin to use AsyncLLM and async_completion
• Update tests to handle async operations

The main changes were:

1. Replacing LLM with AsyncLLM in imports and type hints
2. Making methods async that use LLM completion
3. Replacing completion() calls with async_completion()
4. Updating tests to handle async operations

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:74fff3f-nikolaik   --name openhands-app-74fff3f   docker.all-hands.dev/all-hands-ai/openhands:74fff3f