[Feature]: Allow setting of `SANDBOX_ENV` variables from config.toml

[neubig]

What problem or use case are you trying to solve?

It is possible to set environmental variables in the sandbox through environmental variables in the environment, pre-pended with SANDBOX_ENV: https://github.com/OpenDevin/OpenDevin/blob/beb74a19f607e7fa2d1c2581373fc7ec1409ffeb/opendevin/runtime/sandbox.py#L12-L16

I expected that I would also be able to set the same variables through config.toml, but apparently this does not work.

Describe the UX of the solution you'd like

It would be good if we could set the variables through config.toml as well. This can be done by modifying the code above, or possibly modifying the file opendevin/core/config.py