Scan v2

[pditommaso]

This PR implements several enhancements in the scan capability. More in details:

• Run scan for any container request (not only builds)
• Make scan strategy configurable:
  • none (no scan, default?)
  • async (run a scan on container request, no blocking)
  • sync (run a scan on container request, scan should pass to make the container accessible)
• Allow specify allow security vulnerability levels to pass the scan e.g. low, medium
• Introduce a new container request status endpoint to check requests status GET /v1alpha2/container/{requestId}/status that returns those statuses:
  • PENDING
  • BUILDING
  • SCANNING
  • DONE

Corresponding PR on Wave CLI