Link to diff from comment in pull request overview should go to line

How to reproduce:

1. Create a pull request with multiple changes to a file (hunks)
2. Add a line comment at the bottom of the diff
3. Go to the overview and find the comment that was just added
4. Click on the file name that links to the diff

Expected: The diff is opened with the file, with the part of the diff where the comment is in view.
Actual: The diff is opened with the file, but the top of the diff is in view

Because of the current behavior, the user has to find the comment manually by scrolling to it or using the browser's find functionality.

(This was derived from STASH-4190, and implementing it would make it easier to go to the full diff and expand it there.)