Improve har:view to show info on the spot that was found.

[nedtwigg]

• har:view now displays the CommentSpot instances it created, and on which textarea that was done
• what this reveals is that we are double-annotating in a lot of places
  • e.g. on IssueAddComment and PRNewComment we were enhancing the correct commentbox and also the feedback box
• now the tests are more rigorous, we snapshot every textarea, and we expect some to be enhanced and some to not be enhanced, and we support both
• what this also revealed is a deeper problem in how we are testing IssueAddComment
  • in a real browser, there are two textboxes, and we were annotating both (the correct one and a feedback one)
  • but in our unit test, there was only one textbox
  • this is because the real comment textbox is not present on page load, it only shows up dynamically
  • so it worked in a live browser because we were annotating two textboxes and getting away with it (dumb luck)
  • and in the unit test, the only one we were annotating was the wrong one
  • our HAR infrastructure is currently incapable of unit-testing the basic "Issue Add Comment" workflow
• summary: in this PR we made har:view and unit tests a bit more rigorous, which exposed some problems that will get fixed in later PRs.