This revision adds a Mentions tab to the revision between the History and Commits tabs
The tab functions exactly like the tab you see on a Maniphest task
The reason for this change is that when you have revisions that have lots of activity, or, lots of mentions in other places (including tasks, and other revisions) it is hard to see that list in a concise way
For discussion
- Should we extend this to other objects? - And if so, do we need to make this reusable in some way?
- Does the tab order matter or is between `History` and `Commits` just fine?
Closes T16003