[Chore] Add fallback to Personal Access Token if Installation Access Token fails for whichever reason

[LeoColman]

In a thread on slack we discovered that for some unknown reason the GitHub App might be timing our app out.

To mitigate this issue a little, we should cascade failing App requests to request with PAT, as we originally used to do.

• Add fallback to PAT
• Add logs for when IAT fails
• Add a metric for when IAT fails