Forward SIGTERM to underlying opentofu process to stop getting locked when you cancel a workflow

[arianvp]

Currently if you cancel a workflow run it causes the tofu plan to kill ungracefully and cause your state to not get unlocked. I think it's because signals are not properly forwarded.

[abstractionfactory]

Hello and thank you for this issue! The core team regularly reviews new issues and discusses them, but this can take a little time. Please bear with us while we get to your issue. If you're interested, the contribution guide has a section about the decision-making process.