Add management command to check for multiple parent types

Adding a way to check which domains have multiple options set so we can see how much needs to be fixed before merging the commit to actually prevent this.
i think you also want the location types spit out here since this is likely going to dump a bunch of stuff that is just a result of the default hierarchy supporting multiple parentage forever.

to make analysis easier, i'd also recommend converting this to csv, and adding some domain metadata to the export (for example the `is_test` property will be useful). it might also be useful to add the number of matching locations of that type (since if that number is 0 it likely doesn't matter)