Merge suggest-reviewers into maintainer-approval as a single workflow

The suggest-reviewers workflow posted a comment with reviewer suggestions
based on git history. The maintainer-approval workflow checked approval
status and set a commit status. This merges both into one workflow so
every PR gets a single comment that shows both approval status and
reviewer suggestions.

Changes:
- maintainer-approval.js now scores contributors via git history and
  posts a comment with approval status per ownership group, reviewer
  suggestions, and eligible reviewers. Uses delete-then-create for
  comments so they always appear at the bottom.
- maintainer-approval.yml gets pull-requests:write, contents:read,
  fetch-depth:0 (full history for git log), and skips drafts.
- Deleted suggest-reviewers.js and suggest-reviewers.yml.
- Updated test-owners-scripts.yml to remove suggest-reviewers path.
- Added 7 new tests for comment posting (marker, delete-then-create,
  per-group, single-domain, all-approved formats).

Co-authored-by: Isaac

Author: simonfaltum