Refactor latest.py and update.py (#270)

- create new gha.py module,
- improve GitHub workflow commands (GITHUB_OUTPUT, GITHUB_STEP_SUMMARY) interactions,
- improve logging,
- split update.py into smaller functions.

.github/workflows/update.yml

@@ -77,6 +77,6 @@ jobs:
           commit_author: 'github-actions[bot] <github-actions[bot]@users.noreply.github.com>'
 
       # we still want to easily know if something went wrong
-      - name: Set job status
+      - name: Restore update.py failure
         if: steps.update_data.outcome != 'success'
         run: exit 1