feat: tee command output to stdout/stderr in /execute_action endpoint

[rbren]

This PR adds functionality to tee the command output to both the response and the real stdout/stderr in the /execute_action endpoint. This is useful for debugging and monitoring command execution in real-time.

Changes:

• Modified BashSession._continue_bash to print output character by character in real-time
• Added real-time output printing with print(char, end="", flush=True)
• Modified run and run_ipython methods to print their output to stdout
• Added flush=True to ensure output is written immediately

The changes ensure that:

1. Command output appears in real-time on stdout/stderr as it is being produced
2. The same output is collected and returned in the response
3. Long-running commands can be monitored in real-time while still getting the full output in the response

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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:0054ef7-nikolaik   --name openhands-app-0054ef7   docker.all-hands.dev/all-hands-ai/openhands:0054ef7