Docker prune fails if image is both used for resource and as base image

Expected Behavior

• tilt docker-prune should be able to clean up all images Tilt produced

Current Behavior

• tilt docker-prune can fail to remove images if it tagged them more than once

  [Docker Prune] cannot prune image sha256:eb853b9faada7b43bb19f47affd56b0c9db75b182fd2d7bf8df21389f1943d29 (tags: monolith-worker-tilt_docker_build_with_restart_base:tilt-eb853b9faada7b43, monolith:tilt-eb853b9faada7b43); `docker image remove --force` required to remove an image with multiple tags (Docker throws error: "image is referenced in one or more repositories")
  

Steps to Reproduce

1. Create a Tiltfile with at least 2 docker_builds where the second one uses the first one as base image

   load("ext://restart_process", "docker_build_with_restart")
   docker_build("monolith", ".")
   docker_build_with_restart("monolith-worker", ".", dockerfile_contents="FROM monolith", entrypoint="<omitted>")
   docker_prune_settings(disable=False, max_age_mins=1, num_builds=1, keep_recent=1) 
   ...
   # bring up some k8s resources that use those images above
   

   N.B. You need a Pod with BOTH monolith AND monolith-worker
2. Run tilt up, build a few times
3. Stop Tilt, run tilt docker-prune

About Your Use Case

From Allon Hadaya in #tilt

Start at the tilt docker-prune entry point and reproduce the case with two docker_builds where the second uses the first as its base image, plus a Pod using both images. Verify the fix by running tilt docker-prune after repeated builds and confirming that all eligible images are removed without requiring docker image remove --force.