zarf package mirror-resources should either default to the zarf registry / zarf git server or require either --registry-url or --git-url

[AustinAbro321]

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

Running zarf package mirror-resources without any CLI options may be confusing to users as the error message looks like this currently.
registry:

 WARNING  Retrying (1/3) in 5s: GET
          https://index.docker.io/v2/stefanprodan/podinfo/manifests/6.4.0-zarf-2985051089:
          MANIFEST_UNKNOWN: manifest unknown; unknown tag=6.4.0-zarf-298505108

git repo:

 WARNING  Retrying (1/3) in 5s: failed to push the git repo "zarf-public-test-1143224168": unable to
          push repo to the gitops service: repository not found

Users might expect that we default to the zarf registry / server or they may think something is wrong with their package or images. Likely we should either default to the zarf registry and zarf git server or fail if those are not set and they are using them

Describe the solution you'd like

• Given I have a package that has images
• When I run zarf package mirror-resources zarf-package-my-package without specifying the --registry-url
• Then I get an error message "zarf package mirror-resources requires registry to be set to mirror images`
  OR
• Given I have a package that has images
• When I run zarf package mirror-resources zarf-package-my-package without specifying the --registry-url
• Then the images are uploaded to the zarf registry

Similar for the git repo use case but repos instead of images and --git-url rather than --registry-url

Additional context

IMO it makes sense to default to the Zarf registry and git server if it exists as that is likely the majority of the use cases for this command