[12.x] Add ability to run callbacks after a response

[cosmastech]

While we can add middleware to the Guzzle stack, it doesn't actually build the Response object, which I would like to inspect and mutate.

1. I want to record GraphQL query costs only for Shopify requests. I could add a listener for this, but then it's an extra function call for requests which are not for Shopify.
2. I want to be able to leverage macros and all of the other niceties offered by the Illuminate Client\Request object, rather than mucking with the Guzzle handler.