PR review flow integration: Terraform plan + Ansible dry-run

This is a good time and repository to show the PR flow with BitOps.
https://github.com/bitovi/bitops/issues/325

When using this GH Action, on every PR the terraform should run plan, and ansible should run dry-run,
show the result as a GH Status check.
Once the PR is approved and merged, - run the actual terraform apply.

Bonus points if we could post the `tf plan` diff back to the PR as a comment.

See https://github.com/marketplace/actions/terraform-pr-commenter#screenshots as an example:

StackStorm is a complex beast and allowing users to run the proper PR review flow instead of "I'm feeling lucky" `apply` would prevent users from shooting themselves in the foot and encourage best practices.

从仓库的 GitHub Action 入口点开始，跟踪 Terraform 和 Ansible 部署运行是如何被调用的。围绕 Terraform plan、Ansible dry-run、GitHub status checks 以及合并后的 apply 定义 PR 流程；可选的 Terraform diff 评论属于额外范围。完成的标准是工作流能够安全地区分审查运行与合并后的部署运行。

由索引模型根据 Issue 内容生成。