ability to import an image into k3d when running slim-dev

[cmwylie19]

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

I am running tests against candidate Pepr images in UDS Core and I do not want to have to publish the candidate image to Dockerhub or any other container registry as this slows down the feedback loop.

Additional Feedback Collected:

• This probably does not belong in the `packages/checkpoint-dev/zarf.yaml. It would make more sense in the dev-docs and/or a task.

Describe the solution you'd like

• Given I want to run a test with a Pepr candidate controller image in UDS Core
• When I call uds run ... and I pass in a IMPORT_IMAGE
• Then I want the ability to import that image into the cluster

Describe alternatives you've considered

Make the changes I need locally and not submit a PR to UDS Core.

Additional context

Add any other context or screenshots about the feature request here.