[js-repo-migration] Give Cradle tests a singular home in this repo

[abernix]

With #134, the .feature Cucumber files which lived in apollo-server will now live in this repository. The copies that existed in apollo-server had previously been acting as the single source of truth, but we were copying them (manually) over to this repository in order to verify the conformance of the new Rust query planner.

That means there are now two copies in this repository! We should move them into a (likely, top-level) folder and give them a README on how to use them and remove the duplicated copies in a way that allows the places they are depended on (within this repo) to rely on the single source of truth.

[JakeDawkins]

This is great! Do you think we can version these files in some way? Even if it's a line in the readme? Just to make it easier to track changes

[Enrico2]

When copying over those .feature files from the PR to the Rust repo, we had to change a couple of minor things. The only one that pops to mind is some place with different field ordering where Rust actually did the right thing, once we switch to a single source of truth for the .feature files, we'll need to fix that "bug" in JS.

I think this was the change: 2f81460 (#113)