Make mergebot failure messages more readable (#84214)
Reformat how mergebot outputs merge and revert errors to make the failure more obvious and hide text that doesn't actually help most users debug their PRs. (The workflow job helps the DevX team to debug mergebot errors)
### Old message:
<img width="933" alt="image" src="https://user-images.githubusercontent.com/4468967/187276407-fb35880c-5ada-4f1f-a01e-86b5071ab0fd.png">
### New message contents:
<img width="833" alt="image" src="https://user-images.githubusercontent.com/4468967/187276280-e7397edb-1887-41a2-b206-4d005b59f683.png">
### New message contents detailed expanded:
<img width="843" alt="image" src="https://user-images.githubusercontent.com/4468967/187276342-b50e6b28-f19e-4547-bf29-1a7878a3a97c.png">
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84214
Approved by: https://github.com/malfet, https://github.com/huydhn
