[mergebot] add additional checks (#79317)
We're adding 2 additional checks:
1. If the user has pushed any additional updates to a PR while we're busy waiting.
2. If the user's PR is greater than 3 days old (I think this is the limit on phabricator is the same) we don't let them merge (unless force pushing). Maybe this can be extended to 5 or 7 day if we get a lot of negative feedback.
Check that the script still runs with these additional checks using dry run
<img width="763" alt="image" src="https://user-images.githubusercontent.com/34172846/173151477-40fd1779-fc8b-4d92-b393-2e2fcc456259.png">
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79317
Approved by: https://github.com/seemethere
