Use ubuntu-slim for lightweight release jobs
Move matrix preparation, release management, and artifact packaging to `ubuntu-slim`, as suggested in #7080. These jobs use shell tools and release APIs and do not require multiple CPU cores. Compilation jobs retain their existing runners.
The change consists of six runner-label replacements and my first-contribution entry in `AUTHORS`. No functional change.
Validation:
- `actionlint` passes for the candidate workflows (ShellCheck integration disabled).
- [Fork validation](https://github.com/ofelixdev/Stockfish/actions/runs/34765627178) runs the affected steps on both `ubuntu-latest` and `ubuntu-slim`, using the eight real compilation artifacts from upstream run [34745589340](https://github.com/official-stockfish/Stockfish/actions/runs/34745589340).
- All eight current packaging variants preserve file contents and permissions across runners. All 32 assets downloaded from the four temporary releases match the uploaded archive SHA-256 values.
- Matrix outputs, real draft creation, previous-prerelease selection/deletion, uploads, and prerelease publication pass. Release-script checks cover 45 cases on each runner; the archive verifier has 13 tests on each runner.
The validation harness is on a separate branch in my fork and is not included in this patch. It uses fork-specific tags and repository bindings; the engine is not rebuilt by this validation.
AI assistance was used for the patch and validation tooling.
Fixes #7080.
closes https://github.com/official-stockfish/Stockfish/pull/7166
No functional change