[change-detection] Determine if tf entrypoint has changed on base branch and block

### TL;DR

Some guardian repositories will have many terraform entrypoints. Most of which can be actuated independently. It would be beneficial if it was possible to detect changes in guardian that require rebasing instead of enforcing rebasing with the repo level setting as this can add a bit of overhead to the process (especially if the repo is sufficiently large and has many engineers working on it).

### Detailed design

Not sure if there is a good solution here. I think the main obstacle is that you can ensure on pull_request triggers that everything is up to date for the directory you are working in - however, determining if something has changed in between the last trigger and merge is more difficult. We could introduce merge queue here with a single check that confirms that the base branch and PR branch are indeed up to date.

### Alternatives considered

_No response_

### Additional information

_No response_