refactor(client-lib): remove old aggregator client
about integration tests: - this induce an regression for them as there's no longer the `AggregatorRequest` type to get the route without a magic string, and the queries from the aggregator client crate don't expose their route either. Avoiding magic strings this would require to expose the queries route in a way or another (with a test extension trait for example), but is it worth the additional code ?