Disallow removing pull-through remotes when referenced from a pull-through distribution

[git-hyagi]

Version

    {                                                                                                                                                                                                                                                                                     
      "component": "core",                                                                                                                                                                                                                                                                
      "version": "3.57.0.dev",                                                                                                                                                                                                                                                            
      "package": "pulpcore",                                                                                                                                                                                                                                                              
      "module": "pulpcore.app",                                                                                                                                                                                                                                                           
      "domain_compatible": true                                                                                                                                                                                                                                                           
    },                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
    {                                                                                                                                                                                                                                                                                     
      "component": "container",                                                                                                                                                                                                                                                           
      "version": "2.22.0.dev",                                                                                                                                                                                                                                                            
      "package": "pulp-container",                                                                                                                                                                                                                                                        
      "module": "pulp_container.app",                                                                                                                                                                                                                                                     
      "domain_compatible": false                                                                                                                                                                                                                                                          
    }

Describe the bug
Removing a pull-through remote that is already associated with a pull-through distribution will cause errors during an image push:
#1727 (comment)

...
   File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 637, in get
     raise self.model.DoesNotExist(
 pulp_container.app.models.ContainerDistribution.DoesNotExist: ContainerDistribution matching query does not exist.
...
   File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 637, in get
     raise self.model.DoesNotExist(
 pulp_container.app.models.ContainerPullThroughRemote.DoesNotExist: ContainerPullThroughRemote matching query does not exist.

To Reproduce
Steps to reproduce the behavior:

REMOTE_HREF=$(curl -sH 'content-type: application/json' -uadmin:password -XPOST http://localhost:5001/pulp/api/v3/remotes/container/pull-through/ -d '{"name": "foo", "url": "https://quay.io"}' | jq .pulp_href)
curl -H 'content-type: application/json' -uadmin:password -XPOST http://localhost:5001/pulp/api/v3/distributions/container/pull-through/ -d '{"remote": '${REMOTE_HREF}', "name": "quay-cache", "base_path": "quay-cache"}'
curl -sH 'content-type: application/json' -uadmin:password  http://localhost:5001/pulp/api/v3/remotes/container/pull-through/|jq '.results[]|.pulp_href' | xargs -I{} curl -sH 'content-type: application/json' -uadmin:password  http://localhost:5001{} -XDELETE
podman pull pulp-container:5001/quay-cache/pulp/pulp-web:stable

Expected behavior
We will handle the exception through #1727, but, in addition to that, we could also deny the removal of the remote if it is already referenced by a distribution.