pr-auditor: change token, improve diagnostics and filtering
Created by: bobheadxi
Looking through https://github.com/sourcegraph/sourcegraph/actions/workflows/pr-auditor.yml?query=is%3Afailure for an initial round of fixes:
- Switch to token that should have access to open issues in another repo
- Improve readability of logs
- Improve filtering of events to handle
Test plan
n/a