Modpack deployment enhancements

[tbeswick96]

• Add ability to rollback a release (currently manual by deleting repo and keys contents and copying from backup)
• Use HEMTT to build (UKSF, F-35, ACE, ACRE) when mature enough
• Change release flow to promote a build through the different envs
  • TBD
• Expand guard to block build queue processing whilst a server using that environment repo is running (build should run when server stops). Requires Expand servers integration #144
  • Evaluate performance impact on running servers of a build running
  • Can API resource usage for builds be dynamically scaled if a server is running?