Make result optional on webhook splits

[rowanseymour]

By changing the router to not use the result.

We currently construct webhook routers like:

{
        "type": "switch",
        "operand": "@results.cat_fact.category",
        "cases": [
            {
                "uuid": "190c8a9d-2a22-497a-9bc8-3f11c4af56c3",
                "type": "has_text_eq",
                "arguments": [
                  "Success"
                ],
                "category_uuid": "a8ddc734-6b34-444b-b30b-9838615a095e"
            },
            {
                "uuid": "ff810df6-23c2-4dff-9be1-eebffae2bb9d",
                "type": "has_text_eq",
                "arguments": [
                  "Failure"
                ],
                "category_uuid": "a8ddc734-6b34-444b-b30b-9838615a095e"
            }
        ],
        "categories": [
            {
                "uuid": "a8ddc734-6b34-444b-b30b-9838615a095e",
                "name": "Success",
                "exit_uuid": "d7488301-2b2a-4562-9d22-3dfb7bef0600"
            },
            {
                "uuid": "5f2c6bb7-0473-4ff1-abf0-5199c0ff87a9"
                "name": "Failure",
                "exit_uuid": "251a9293-85c2-473a-b302-c0f79624d9bb"
            }
        ],
        "default_category_uuid": "5f2c6bb7-0473-4ff1-abf0-5199c0ff87a9"
    }

We would construct them like this instead:

{
        "type": "switch",
        "operand": "@webhook.status",
        "cases": [
            {
                "uuid": "190c8a9d-2a22-497a-9bc8-3f11c4af56c3",
                "type": "has_number_between",
                "arguments": [
                  "200",
                  "299"
                ],
                "category_uuid": "a8ddc734-6b34-444b-b30b-9838615a095e"
            }
        ],
        "categories": [
            {
                "uuid": "a8ddc734-6b34-444b-b30b-9838615a095e",
                "name": "Success",
                "exit_uuid": "d7488301-2b2a-4562-9d22-3dfb7bef0600"
            },
            {
                "uuid": "5f2c6bb7-0473-4ff1-abf0-5199c0ff87a9"
                "name": "Failure",
                "exit_uuid": "251a9293-85c2-473a-b302-c0f79624d9bb"
            }
        ],
        "default_category_uuid": "5f2c6bb7-0473-4ff1-abf0-5199c0ff87a9"
    }