Add gate visualisations for `OpType.CnRx` and `OpType.CnRz`

[CalMacCQ]

The CnRx and CnRz gates have been added in pytket v1.29. The CnRy gate has been a member of OpType for sometime and has the following visualisation.

Currently CnRx and CnRz look like boxes. It would be nice to update them.

[DNA386]

#63