Add Blaxel support for remote code execution

[Joffref]

Summary

• Introduced BlaxelExecutor for executing Python code in Blaxel sandboxes, leveraging fast-launching VMs with hibernation.
• Updated pyproject.toml to include Blaxel as a dependency.
• Modified documentation to reflect Blaxel integration across installation steps, usage examples, and security considerations.
• Updated CodeAgent to support executor_type="blaxel".
• Added unit tests covering BlaxelExecutor.

Open Questions

• Do we need to embed a specific set of dependencies directly into the sandbox image for consistent execution?
• What is the recommended way to test this implementation end-to-end (beyond the unit tests already added)?

[Hugoch]

Hey @Joffref , thanks for the contrib! Seems that your code is not handling the final answer as expected

Execution logs:
Traceback (most recent call last):
  File "//run-code.py", line 14, in <module>
    final_answer(fib_100)
    ^^^^^^^^^^^^
NameError: name 'final_answer' is not defined

Final answer: Traceback (most recent call last):
  File "//run-code.py", line 14, in <module>
    final_answer(fib_100)
    ^^^^^^^^^^^^
NameError: name 'final_answer' is not defined

Also sandbox cleaning seems to take a lot of time, is that expected? Do we need to wait?

[Joffref]

Hey @Hugoch, thank you for reviewing this!

Regarding the deletion time — we do need to wait until the deletion has been completed, since names can collide and cause errors when trying to deploy a new sandbox with the same name.

For the error you’re seeing, would you mind sharing the code you used, or the snippet/code I can run in the SDK to test my implementation properly?