graphiql should be full page in lab

[saihaj]

[dotansimha]

Also, @B2o5T, I think we had a Connect button here in the older design? that shows a modal with the instructions for using the Hive schema with other tools. I think we can drop the old Lab-specific token and setup we have, and just point the users to use the CDN schema instead? (we can reuse the same modal and instructions from the Schema page, just point to a different CDN link (should be /introspection or /sdl instead of the default root CDN endpoint)