workspace actions: amend workspace job to cleanup workspaces

[Kira-Pilot]

• repurpose existing job (perhaps autobuild package) to handle all workspace lifecycle actions
• add new action: delete workspaces marked for deletion
• add new action: stop workspaces marked as failed
• Ensure we have some sort of automatic signaling for upcoming deletions, auto-offs, and auto-ons. These will be consumed by VS Code (see workspace actions: add VS Code notifications for workspace messaging #7360)

[sreya]

closed by #8240