Instance NIC list method might be authorizing against the wrong parent

While working on adding the IP version to our IP Pool objects, I found this:

https://github.com/oxidecomputer/omicron/blob/dab669342984908b1efd08df5a05830387c07afb/nexus/db-queries/src/db/datastore/network_interface.rs#L888-L894

This seems to be doing an authorization check on our builtin Oxide services IP Pool, while we're listing the interfaces attached to instances. Those use a separate, customer controlled IP Pool. It seems like we're doing the authz check against the wrong thing here. AFAICT, this is only used in one place, instance_network_interfaces_all_list_batched, which itself seems unused anywhere in Omicron. We could just remove this whole thing entirely, or figure out how to adjust this authz check to be on the right pool.

Start in nexus/db-queries/src/db/datastore/network_interface.rs at instance_network_interfaces_all_list_batched and the authorization check around lines 888-894. Search Omicron for callers to confirm whether the method is unused, then determine whether removing it or correcting the checked IP Pool is appropriate. Done means the listing path no longer authorizes against the wrong parent and its callers remain valid.