Use SewingKitKoa Middleware in createRender

[cartogram]

Description

This PR adds Sewing Kit Koa's middleware to the createRender middleware in @shopify/react-server. createRender is already tied to the Sewing Kit Koa middleware, this just makes it so users have less to do in their Koa server/ are less likely to hit errors when trying to use it.

The createRender middleware now accepts an assetPrefix that is passed to the sewingKitKoa middleware.

Type of change

• @shopify/react-server Major/Breaking

Checklist

• I have added a changelog entry, prefixed by the type of change noted above

[marutypes]

This looks good to me, we just need to make sure it's marked as a breaking change and that existing uses are fixed to not mount the koa middleware manually.