CI: Automate backport process more

[leofang]

We have a backport bot but it does not always work:

• Any PR touching files under .github/ cannot be backported by the bot due to permission issues
• cuda.bindings most of the time needs to be regenerated, so a naive backport does not always work either

[leofang]

• Any PR touching files under .github/ cannot be backported by the bot due to permission issues

To remind myself why it hasn't been fixed: This is a typical error message from the backport bot

git push --set-upstream origin backport-1106-to-12.9.x
To https://github.com/NVIDIA/cuda-python
 ! [remote rejected] backport-1106-to-12.9.x -> backport-1106-to-12.9.x (refusing to allow a GitHub App to create or update workflow `.github/workflows/ci.yml` without `workflows` permission)
error: failed to push some refs to 'https://github.com/NVIDIA/cuda-python'

which means for the bot to work it needs the workflows permissions (specifically, I am guessing workflows: write). However, based on the docs we can't grant GITHUB_TOKENS such a permission. It seems a more complex solution is needed to work around the permission issue.