refactor(ci): standardize Stale Action config

[agilgur5]

Motivation

• fix OpenSSF Scorecard issues
• have consistent settings here as in Workflows

Modifications

• fix OpenSSF Scorecard issues

  • set top-level permissions to read-only
  • add comments for job-level permissions
  • pin action to a SHA

• use same settings as Workflows

  • with a dedicated stale-issue-message & stale-pr-message
  • same cron schedule
  • same formatting: indentionation and ordering etc

Notes to Reviewers

This will merge conflict with #549 (due to indentation etc changes), so it is a draft for now

[agilgur5]

This will merge conflict with #549 (due to indentation etc changes), so it is a draft for now

Rebased on top of #549 and fixed all merge conflicts, ready for review now