Update json decoder

[aborgna-q]

Now using OpDefs and a TKET1 resource.
The logic for translating individual operations is contained by an internal JsonOp struct, which tries to make things as homogeneous as possible (given that any data in an tket_json_rs::Operation may be missing).

Next up is doing the encoder and testing the roundtrip. This should be straightforward now that we have the Commands iterator.

Note that free variables as parameters are not yet supported. (That'll probably go into an issue after this is merged.)

---

Note that until we solve CQCL/hugr#263 printing the graph will not show the actual name of wrapped operations:

Alternatively, we could dynamically add operations to the resource when we encounter new unsupported operation names. I'm not sure whether non-static resources would break something in the hugr...

[ss2165]

👍