ci: Add expiry tags to scale test cloud infra

[learnitall]

This issue tracks adding expiry tags to the infrastructure deployed by scale test workflows. Cloud Custodian can use these expiry tags to clean up dangling VMs and clusters in a scenario where cleanup within a workflow fails.

cc: @marseel, @nbusseneau

[github-actions]

This issue has been automatically marked as stale because it has not
had recent activity. It will be closed if no further activity occurs.