fix(github-pull-requests): introduce max 1000 item paging

[dzemanov]

Description

GitHub Search API has limit of max 1000 results.
This causes 422 errors when the search returns more than 1000 items.

{
  "message": "Only the first 1000 search results are available",
  "documentation_url": "https://docs.github.com/v3/search/",
  "status": "422"
}

Modifications

Restrict pagination to a maximum of 1000 items. Show users when additional results are available, suggesting in a tooltip that they can refine their query to retrieve more specific results.

Before:

After:

demo.mp4

Fixes

#1596

✔️ Checklist

• Added tests for new functionality and regression tests for bug fixes
• Added changeset (run yarn changeset in the root)
• Screenshots of before and after attached (for UI changes)
• Added or updated documentation (if applicable)