Cannot use directional CX tket pass on its own

[jfriel-oqc]

In the compiler config, the use of directional gate only doesn't not work.

This is a common user request as many users want to map to the topology, but don't want to do the directional gate pass. We need to allow this and verify that the circuit respects the topology

[rodrigo-oqc]

It would be interesting too if the SWAP gates are also applied in the routing process. The common request is just a way to select the qubits being used while not worrying about topology or routing. DirectionalCXGate can be used together with RoutingPass in Tket, but, I believe, RoutingPass does not allow the user to select the set of qubits that they want to use