id_queue: Expose full and empty status

[colluca]

Creates an empty signal to track when the linked data table is empty, and exposes both the empty and full signals at the interface of the module.

[phsauter]

Exposing the full signal is free and the empty signal costs a reduce-AND but only if used.
@niwis why is this marked as v2? It changes the interface but is fully backwards compatible since it is legal to leave out unconnected outputs in the instantiation.

[niwis]

To me, interface changes implied a major release. If missing outputs are supported by the standard tools, feel free to bend that rule.