result extension not exposed as ExtensionOp

[qartik]

The recent result extension added in #494 seems to not be exposed as an ExtensionOp but only as opaque, ie, as_extension_op() returns None on a node containing the result HUGR.

Here's a sample HUGR that I was trying to process via hugr-llvm:

&args.node().as_ref() = Opaque(
    OpaqueOp {
        extension: IdentList(
            "tket2.results",
        ),
        name: "Result",
        description: "",
        args: [
            Type {
                ty: TypeBase(
                    Sum(
                        Unit {
                            size: 2,
                        },
                    ),
                    Copyable,
                ),
            },
            BoundedNat {
                n: 0,
            },
        ],
        signature: FuncTypeBase {
            input: TypeRowBase {
                types: [
                    TypeBase(
                        Sum(
                            Unit {
                                size: 2,
                            },
                        ),
                        Copyable,
                    ),
                ],
            },
            output: TypeRowBase {
                types: [],
            },
            extension_reqs: ExtensionSet(
                {},
            ),
        },
    },
)

[aborgna-q]

Turns out this is a bug in guppy.
The extension name should be tket2.result (without an s), and the operation should be called result_uint

See CQCL/guppylang#367