Admin listing of API backends limited to first 50 results with no pagination

[GUI]

In the admin tool under "API Backends" the listing of backends is capped at 50, and the pagination is non-functional. We now have 67 API backends, but you wouldn't know it based on the pagination:

At this point, this only really affects the superuser admins on the api.data.gov team that have access to all of the APIs, since agency admins will typically only have access to a few of their own APIs.

It's still possible to get to the other APIs by flipping the sort order or by searching, which returns to the hidden APIs, but it's certainly incorrect and confusing.

Pagination seems to be working in all the other pieces of the admin, so I suspect we're just doing something silly to break this on the API backends listing.

[GUI]

Fixed and tests added NREL/api-umbrella-web@1ef237f