fix(ci): clean up destination folder on unstable and testing delivery

[kduret]

Summary

• Extend the existing cleanup step to also run on unstable deliveries (previously only applied to testing)
• Rename the step from "Clean existing testing packages" to "Clean existing packages"
• For DEB packages, the release_type property filter is only applied when stability is testing (not applicable for unstable)

Test plan

• Trigger an unstable delivery and verify old packages are removed from the destination folder before the new ones are uploaded
• Trigger a testing delivery and verify existing behaviour is preserved (cleanup still runs with release_type filter for DEB)
• Trigger a stable delivery and verify the cleanup step is skipped

🤖 Generated with Claude Code

Summary by Aikido

Security Issues: 0	Quality Issues: 0	Resolved Issues: 0

⚡ Enhancements

• Extended cleanup step to run on unstable and testing deliveries
• Applied DEB release_type filter only when stability was testing

🔧 Refactors

• Renamed cleanup step and addressed actionlint formatting issues

^{More info}

[github-actions]

Checkmarx One – Scan Summary & Details – 077ddb52-4441-41c8-aff9-37a652773eec

Great job! No new security vulnerabilities introduced in this pull request