Refactor I/O utils; allow 'task' command line parameter in cli.py

[enyst]

End-user friendly description of the problem this fixes or functionality that this introduces

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Give a summary of what the PR does, explaining any non-trivial design decisions

This PR proposes:

• dedup CLI utils in their own utils/io.py
• fix task argument in cli.py

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Link of any specific issues this addresses
Fix #5719

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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:7634d4b-nikolaik   --name openhands-app-7634d4b   docker.all-hands.dev/all-hands-ai/openhands:7634d4b