Change entities REST order to match OData order

[ktuite]

Closes getodk/central#582

What has been done to verify that this works as intended?

Tests

Why is this the best possible solution? Were any other approaches considered?

The ../entities REST endpoint was returning entities ordered by entity def id, which doesn't seem very meaningful. That part has been removed and now entities are returned in a stable order that matches the odata endpoint.

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

I hope no one is relying on that other weird order. It wasn't documented.

Does this change require updates to the API documentation? If so, please update docs/api.md as part of this PR.

We could keep not documenting the order here. The odata endpoint has a more explicit and controllable query param for ordering entities.

Before submitting this PR, please make sure you have:

• run make test and confirmed all checks still pass OR confirm CircleCI build passes
• verified that any code from external sources are properly credited in comments or that everything is internally sourced