Instantiation fails for ArrayOps with non-prelude element type

[aborgna-q]

Failing test case, similar to array_op::tests::test_get.

    #[test]
    /// Initialize an array operation where the element type is not from the prelude.
    fn test_non_prelude_op() {
        let size = 2;
        let element_ty = float64_type();
        let op = ArrayOpDef::get.to_concrete(element_ty.clone(), size);

        let optype: OpType = op.into();

        let sig = optype.dataflow_signature().unwrap();

        assert_eq!(
            sig.io(),
            (
                &vec![array_type(size, element_ty.clone()), usize_t()].into(),
                &vec![option_type(element_ty.clone()).into()].into()
            )
        );
    }

This should get fixed if we remove the extension registries from validation.