[Task]: Sort examples and categories on the backend or in the view

### What needs to happen?

Currently examples and categories are sorted on the frontend when parsing the response from the backend:
https://github.com/apache/beam/blob/cea122724c5cd87a403684004452305ca64b3a68/playground/frontend/lib/modules/examples/repositories/example_client/grpc_example_client.dart#L296

This is not an appropriate location, because if we introduce other clients, the experience will be inconsistent.

If we want the user to sort the examples as they wish, the sorting should be in the widget. Otherwise it should be in the backend.

### Issue Priority

Priority: 3

### Issue Component

Component: beam-playground