[RFE] Allow hauler to pull from a registry for images

[zackbradys]

Is your feature request related to a problem? Please describe.

• Yes, see below

Describe the solution you'd like

• For hauler to have the ability to set a registry to automatically prepend to any image

zackbradys@Zacks-MBP ~ % hauler store add image -h
Add an image to the content store

Usage:
  hauler store add image [flags]

Flags:
  -h, --help              help for image
  -k, --key string        (Optional) Path to the key for digital signature verification
  -p, --platform string   (Optional) Specific platform to save. i.e. linux/amd64. Defaults to all if flag is omitted.
  -r, --registry string   (Optional) Specific registry to pull images. Defaults to "docker.io"

Global Flags:
      --cache string       Location of where to store cache data (defaults to $XDG_CACHE_DIR/hauler)
  -l, --log-level string    (default "info")
  -s, --store string       Location to create store at (default "store")

apiVersion: content.hauler.cattle.io/v1alpha1
kind: Images
metadata:
  name: hauler-content-images-example
  platform: linux/amd64
  key: carbide-key.pub
  registry: rgcrprod.azurecr.us
spec:
  images:
    - name: longhornio/longhorn-ui:v1.5.1
      platform: linux/amd64
      key: carbide-key.pub
      registry: rgcrprod.azurecr.us

Describe alternatives you've considered

• Manually maintaining separate hauler manifests with the registry set at each image.
• Manually ensuring that I have the correct registry, in the image name, with each hauler store add image.

Additional context

• N/A

[zackbradys]

Closed per #173!