Consolidate GitHub helpers for community scripts (#63198)

It's been fun for a while to have the same function calling GitHub API
in every single script, but we're going to have fun in different ways
now.

This one's for you, @MrSubidubi! 🥂 

## Testing

I've ran the things that had `--dry-run` locally and nothing blew up,
but the ultimate smoke test will be carried out in production.

---

Release Notes:

- N/A

.github/workflows/comment_on_potential_duplicate_issues.yml

@@ -31,7 +31,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5.0.1
         with:
-          sparse-checkout: script/github-check-new-issue-for-duplicates.py
+          sparse-checkout: |
+            script/github-check-new-issue-for-duplicates.py
+            script/github_helpers.py
           sparse-checkout-cone-mode: false
 
       - name: Get github app token