Fix viewing outdated comments in pull request reviews

[jcansdale]

Navigating to an outdated comment from a pull request review is currently broken. This pull request fixes that and also provides a fallback when our comment matching algorithm diverges from the one on dotcom.

What this PR does

• Fix navigation to outdated comments
• Open outdated file if we can't find a line number to place comment thread
• Add logging if something goes wrong

How to test

Opening an outdated comment

1. Open github/VisualStudio pull request 2241 on GitHub pane
2. Click on Reviewers > jcansdale
3. Expand Outdated comments
4. Click on one of the outdated comment links
5. File diff should open with file is state where comment was originally made
6. In-line comment should appear

Opening comment where line positioning algorithm doesn't quite match dotcom

This example uses a comment that dotcom doesn't flag as outdated, but current our line positioning algorithm can't find a line number for it. It will fall back to showing the file as it was when the comment was originally made.

1. Open github/VisualStudio pull request 2241 on GitHub pane
2. Click on Reviewers > jcansdale
3. Click on comment link under Comments
4. File diff should open with file is state where comment was originally made
5. In-line comment should appear
   
6. Click on log.Error(ex, ... and hit Enter
7. Live file should open on same line (notice the lines starting log and operatingSystem have been swapped)
   

What this PR doesn't do

On github.com, Outdated pull requests are clearly marked. I think we should also do this to let users know they're not looking at the latest version of the code. We could also let users know to click on the source and hit Enter to navigate to the latest version.

Fixes #2247

[donokuda]

On github.com, Outdated pull requests are clearly marked. I think we should also do this to let users know they're not looking at the latest version of the code.

I think a lightweight solution would be to add an "Outdated" badge to the parent comment. I'm not sure if it would communicate that someone isn't looking at the latest version of code, but it would at least indicate that the comment they are reading may not be presently relevant.