Add support for fault-equivalent rewrite rules

[boldar99]

Implements several fault-equivalent (FE) rewrite rules, including:

• elim_FE
• color_change_FE
• fuse_1_FE
• unfuse_1_FE
• unfuse_4_FE
• unfuse_5_FE
• unfuse_2n_FE
• recursive_unfuse_2n_FE

Adds support for w-fault-equivalent rewrites via a w parameter for unfuse_2n_FE and recursive_unfuse_2n_FE.

[jvdwetering]

We are currently working on refactoring how the rewrites work in PyZX, so I don't think I would want to merge in a bunch of new rewrites at this point. I think we can keep working on this separately for a while, and also see where it goes before we merge anything into main.
Maybe it even makes sense to have the fault-tolerant stuff be an extension you can install separately rather than having it inside of PyZX? This might no longer be feasible if we also want support for idealised edges though.

[RazinShaikh]

The simple edge is pyzx should be treated as idealized edges as you can do any ZX rewrites freely. Additionally, we should add a new edge type for faulty edges, on which you should only allow fault-equivalent rewrites.

[RazinShaikh]

@y-richie-y told me that he is also working on this so it would be good to coordinate the effort in this direction

[jvdwetering]

Jackie was also working on an implementation of faulty/idealised edges in a different fork 🙃

[RazinShaikh]

Can you set up a discussion channel or forum (I'm not sure but Lia mentioned this in the ZX software meeting) on the ZX discord? It seems less effective to have 3 people working on the same thing in different ways. We can discuss and set up a todo list of features and tasks.

[jvdwetering]

I can't make new channels in that Discord, but I can ask Miriam