Use registry for kernel selection about backend.ai-webui HOT 2 CLOSED

Idea to display complex image references:

• index.docker.io -> "Public"
  • repository prefix "lablup" -> "Lablup"
  • In Docekr Hub, the repository prefix (project name) is always equivalent to the username.
• Our enterprise registry server -> "Enterprise"
  • Customer ID -> "customer-id"
• Other 3rd-party registry server -> "its hostname" + "repository prefix" (if applicable)
  • Maybe we could add a configuration to shorten their labels
• Other features such as NGC-optimized images -> "NGC"

from backend.ai-webui.

Internally we should keep all image reference strings as the canonical one in the following format:
registry/repository:tag
where repository part may contain a username or project prefix with an additional slash, like:
registry/project/repository:tag
registry/username/repository:tag

from backend.ai-webui.